Personally, I would rather be called back when still young and get it over fast, especially for officers. I got called up for my first reservist in camp training when I was in my mid 30s. It was extremely embarrassing for me due to the following...
a) I reported for ICT in my old Temasek Green uniform. I stood out as all the Army by then had already moved on to the camo No. 4 uniform. I was never issued these (will let you know why later). The Encik (RSM) screamed and harassed at me at the front gate when I booked in. He got his come uppance later though.
b) I have not touched an M16 for donkey years. It was embarrassing at my first attempt to strip it in a test.
c) Tactics and doctrines had changed. I had to re-learn. For example, when I was actively serving we had 9 men per infantry section. It all changed by the time I went for my first call up.
d) I was the odd one out. The rest of the battalion had trained together since their NSF days and even the first few years of their reservist. They had a camaraderie which I could not break into until a few years. After-all I was also more than 10 years older than most. In fact for that first ICT I was probably the most hated guy in the battalion.
e) My reservist vocation was completely different from my primary vocation when I was active. As you get older, it is more like the luck of the draw, you get allocated your unit or vocation randomly. I must admit though, that objectively I was trained for my reservist vocation during all the courses I attended before but it was not my primary vocation in my active years.
f) Yes, while most are about 10 years younger and hence fitter, it is still embarrassing and demoralizing when you had to lead them.
Now, in case you are wondering,... I was the battalion commander of the unit I was posted to for my first reservist training. While I was trained as an army officer, I was actually posted to the AirForce (hence never received camo no. 4) and served there. I was one of the youngest to attend Command School and Staff College primarily because I was a sword winner and a scholarship holder (and regular for 4 years). The initial years of bonding with the men especially when I was younger would have help. Also by then I was also well into my career in the corporate world and while most of my classmates and colleagues would have finished their reservist cycle by mid 30s to early 40s, I did not complete mine until my 50s. While it is nice to play soldier and bond with your reservist mates when you are still young, it gets difficult in your 40s when you have other priorities in life (ie career challenges, kids in their teens etc).Not forgetting, age catches up with you too. I was on the holding list for awhile because I did my post grad overseas plus I worked outside Singapore. It would have been great if I was perpetually on the holding list but I guess the country needed their pound of flesh since I was a former regular and had attend staff college (i.e. for Majors).