They are loaded dice, but you are right, you can’t bet on what will happen.
An age difference can matter - positively or negatively, but it doesn’t have to.
When I was 16 I dated a guy in his 20s. Nice guy, not as skeevy as it sounds. But he was really ready for a different type of relationship than I was, and I wanted to sow a few oats. It made a difference - it wasn’t a huge difference - not even ten years - but at that point in life, big difference. I have a good friend who met his wife when he was in his 20s and she was 16 - they’ve been married 20 years now.
It really does depend on the people, as well as the age of the younger partner- at 17 and 35, it’s pretty unlikely that it’s going to be a ‘fair’ relationship- the teenager is very likely to still be too idealistic and still working out who they are and what they want, and can get steamrollered by the older partner.
I have a friend who dated a 31 year old for quite a while at 17, without any age related issues, they split after a while, but stayed friends; but she’s frankly exceptional in being very very secure in herself, and quite capable of looking out for her own interests. I never really mentally tagged her as younger than me, though she was 16 and I was 24 when we met; same goes for the guy, I believe, he doesn’t normally go for younger women.
Once you’re over around 30, it is just the potential age-related illness and early death of the older partner, but you’re likely to go into it with open eyes by that age. It might well be worth it, maybe not. It’s a decision only those involved can really guess.