I agree it's not about age, per se, but rather health & ability. As an example, my inlaws are close in age but far apart in ability to travel. MIL has physical health issues but incorporates into her plans ways to address them. FIL has physical health issues but half the time acts like he's still 23 & in the army. When IRROPS occur, MIL is not savvy like a FTer but she's persistent; she stays engaged in working the problem until it's solved. FIL will throw up his hands after 2 minutes and wait for someone to fix it for him. ...Which, if MIL's not traveling with him, means he's going to sit there a long time.