My biggest concern about retirement: if I am not going out for work, how am I going to be able to hobby??
Any suggestions?

Volunteer and do multiple do good type  things. You then should be able to schedule your good to you in the mix. And it can happen in the most unforeseen places. A friend of mine volunteers for clean-up and maintenance at his church. A younger wife member of the church does also. They have been banging each other twice a week now for three years. Of course if you just want to do the paid, then the multiple volunteering will give you plenty of time out of the house to plan your joyful times.

join a gym and go there regularly. Be sure it’s a gym at which your wife will never want to join you.  Then you can miss an occasional gym workout for another kind of physical activity.  

There are a number of past-times that will give you time out of the house, as well as giving you cover for expenditures.

Mine isn't and I am spending my grandchildren's inheritance.

Can you do any part time contract work (not  really do it, but have a plausible ability.)  

Good idea. One detail...if you want to see travellers to your city, schedule your regular gym sessions between Tues - Friday. Most travellers arrive on Monday (afternoon check in) and check out Friday around noon.

Sign up for classes at the local community center, or rec. I signed my old man up for yoga. Miss a class to go hobby.

as I do… maximum flexibility in scheduling alternate activities, and keeps me going as I venture further into Senior Citizenship.

Develop a reputation and a habit of disappearing for periods and not always answering your phone. Do that not just when your seeing woman. Even when you are at home and your other is calling. Develop a hobby that takes time. Golfing by yourself. Bicycle riding. Hiking. Something you really like and do often enough that if you skip one day its not obvious. Get a part time job. Become a volunteer. Develop a relationship that you are not accountable to your wife for where you will be and for how long. This may not be easy. She may become suspicious and make it difficult. She may start to do the same to you and have fun of her own.  

He bought hiking gear, the whole nine yards.  He took off Saturdays in the morning and came home in the evening.  He always raved to his wife about how great it was to get away to the solitude of the mountains and breathe the fresh mountain air.

Since retirement ~10 years ago, I've developed an interest in Real Estate Investing and have migrated to doing Private Lending, primarily to house flippers/rehabbers - think HGTV.  That provides the opportunity to visit a nearby metro area (I live in a RURAL community) to meet with potential borrowers, or inspect progress on collateral properties, or attend the local REIA meeting monthly.  It has even given me the opportunity to attend weekend seminars with my out-of-town ATF.  And that is a TAX DEDUCTIBLE expense!!!

I would suggest think ahead and plan for travel in your " new hobby or job " .  I compete in AKC competitions and events.  
The events and training are held all over the country, sometimes for weeks at a time. Being able to see numerous top providers across the country is something I could not do with a local hobby.    

No offense to the ladies, but don't you end up seeing a lot of dogs?

This has been an interesting post to read.  

Get a hobby where collectibles are involved like Die Cast Cars (think scale NASCAR type or hot rod types) or model trains. Buy a couple then look for the shows which are now back. Your wife / SO might want to go to one just to see, but trust me, after going with you once, she'll not want to go with you again. Only downfall, these shows are on the weekend. Many ladies are available on weekends.  

Motorcycle shows.  A great way to escape for hours.  I have not tried that one yet, but you got me thinking.

Recreation centers have programs of classes you can take. Look. Google is your friend.

It is a real problem. After retirement my family and friends would include me in their plans since they knew I had all that free time!

Make it a new habit to regularly visit Lowes or Home Depot to check out tools for home projects.  That can explain the lapses in time for when you actually go to see a lady, and always adding an additional $20 or so to your bill in cash back every time you go gives you a way to assemble cash without it visibly coming from the family budget.

Pick up a Lowes or HD gift card and add it to the checkout. It can be used for TER or P-411 dues. Also cash in some circumstances.

I thing I will just continue working for as long as I can.  
Cannot imagine being in a situation when I no longer can easily meet a provider. Everything else is secondary

I use hiking secure in the knowledge that a lot of our parks (DC area) are National Park Service land and large county parks land and they don't much like cell phone towers away from the visitors center or the sound pollution of people who can't do anything without talking to some friend or relative continuously. As a result, they don't have don't have good cell phone service in most of the park.  

I don't hobby at home as the cost for a one shot deal -session is not as desirable as taking a "trip" or adventure to Mexico. For the cost of one session at home, I can usually get two or more down south with GFE, DFK, BBBJ, and DATY. Heck even threesomes can be had for a similar cost.  I live in Norcal and find ways to make it to TJ and other parts, using  work (I'm semiretired) , family, and sport events.  as the rationales. Takes a lot of coordination.  Usually I will do one of the above for one day on a three to four day trip and call/text and take pictures, but then i quickly head down south, usually flying but sometimes driving.  I have separate accounts and credit cards, and I check in daily with the SO. There is always risk of being somewhere you are not supposed to be, including delayed or cancelled plane fights, car accidents or undesirable run-ins or altercations where your SO might figure things out. I also keep my phone off much of the time across the border so that there is not the funny ring tone that she can hear.