In addition the tours you do later might be different than those earlier and even the places you travel could be different. As mentioned, I am fortunate to have taken multi-month trips at ages 29, 34, 38, 44, 50, 53 and 60. The sort of trip I took at age 29 (six week intense ride from Astoria to Portland ME averaging 95 miles/day including rest days) were different than the trips I took at double that age. Both are fine in their own ways but I also feel fortunate to have had the earlier trips. Doing a ride around Australia now would be different than what I did at age 38 since I would have to break the larger gaps into more pieces.