I dont think you can be too old to collect something. Im 37 myself and I enjoy old toys and new ones as well.
i know my only problem is running out of room to display and collect figures at this point.
so here comes ebay and garage sales to thin my collection out and make it more enjoyable.
Maybe the op is worried about people making fun in some situations? I guess i was too around age 14 when i pretty much stopped buying figures for a while until Star Wars and Beast Wars came roaring back in 1995/1996. I think some people can ruin the fun but there is a whole world of people who make things better, like my Dad and family and other transfans.
My youngest older brother actually got me a loose cybtertron figure the past couple christmases although.. they were the exact same figure.
Keeping them both though as long as I can it helps to pass the time.
So I guess my only problem in collecting toys at an old age is having too many and needing to clean them out a bit. Its not as much fun parting with them but it is very healthy to do it.
and when ive made enough space ... voila theres space for something new!
I think they cant even have my toys when they can pry them from my cold dead fingers..
since Ill be back as a zombie toy fanatic