I don't think there's any limit. At 32, I'll often be the oldest person in a hostel dorm room but it's hardly uncommon for me to meet an older backpacker, sometimes much older.
If you want to go and there's nothing stopping you, just go!
I went backpacking around the world for 3 months at 35, had an amazing time and plan to do it again when I can.
I did get private rooms in hostels where I could, my days of 8-16 share bunks are hopefully behind me (though I did get caught out in Portland, Oregon)
My advice would be to look for any organised day trip or group activities organised out of the hostels, hang out in the common room and join in. I had a great time. I did find it a little weird at the start to be close to twice the age of some of the people in the group but nobody really cared except me.
I guess my only other advice is to pace yourself. There's no shame in taking a day off and putting your feet up.
I'm planning on retiring later this year, and can tell you from personal experience that there is no such thing is too old. If you even think that you want to try the backpacker experience, JUST DO IT !!! For the most part the younger people will greet you with open arms and a smile. There is no better way to meet a diverse group of people than to sit and have a drink in a hostel common room.
NEVER IS TOO OLD. I've met some AMAZING 50 year old womans backpacking in latinoamérica! Please do if you want to!!!!!
Also, if you're looking for some inspiration, there are a lot of people who have been backpacking for many years with an online presence who might be helpful for you to check out. The first person who comes to mind for me is Gabriel Traveler on youtube, who has been backpacking since the early '90s and posts videos of his experiences now as a middle-aged backpacker https://www.youtube.com/user/gabejedmo
No age is too old. Last summer, I was on a plane and started talking to the man next to me. He and his wife were in their mid-70s and were just finishing a backpacking trip through South America. He told me about his first backpacking experience ever, in 1962, when he hitchhiked around the Middle East with his brother. Since then, he has been hooked on that kind of travel, because no matter your age, by backpacking you have a much more intimate experience with the place you visit. You don't only see the manicured parts meant for people on tours or in all-inclusive resorts.
The reason that backpacking is often erroneously connected with younger people is because it's a cheaper way to travel, so people with less money often try it, and if they aren't 100% sold on that kind of travel, then they will stop traveling that way when they have more money. But for those who realize that any other kind of travel will seem inauthentic after backpacking, it doesn't matter how much or little money they have, backpacking is the only kind of travel that can truly satisfy their wanderlust. I understand the fear of agism in the backpacking community because of the way it is perceived, but I can assure you that while, sure, I meet plenty of 18-year-olds on gap year while backpacking, I also always meet people who have been backpacking for decades, or have wanted to backpack for decades and are finally doing it.
I took my parents (who are in their 60s) backpacking for their first time recently and I'll admit I was nervous about what they would think or how they would handle it. But they absolutely thrived. Their favorite parts of the trip were locals they were able to meet and truly get to know by traveling in that manner and the other travelers they met in hostels from all over the world. They're now hooked and say they wish they had given it a try sooner but hadn't felt like that sort of travel was an option once they had reached middle age. They are still in contact with many of the other backpackers they met who inspired them on that trip.
All of this is to say, absolutely go for it. If this feels like the right kind of travel for you, you owe it to yourself to have that experience.
The dot dot dots had me in so much suspense 😅My opinion is that there is no upper age limit but it's all about how comfortable you feel with it yourself! At the end of the day, everyone goes backpacking to have a good time on a budget, to meet new people, experience new things and explore new places. If you're happy to have those experiences with other people of any age then you're not too old!
There are of course always compromises, for example - the older I get, the more inclined I am to get a private room in a hostel over a dorm room for my own comfort and privacy.