Not sure why you posted a question as you seem to think you know the answer.
You want re assurance that a 20 year age difference is acceptable... well okay, think it through.
At 16 is it okay to have a 36 year old partner without judgement from parents and friends?
At 50 do you want a 70 year old partner?
At 60, which these days is still young, do you want to be looking after an 80 year old?
If you feel you are mature at 22 and that having a 42 year old partner is comfortable, why worry?
A bit of fun and experience along the way is what moulds us into the adults we become. However, you already realise that this is what it is... experience!
Most 42 year old women I know have partners of 22-35, very few have partners of 62!
Sorry to put it so bluntly, but if you are honest, you know yourself when you are in the driving seat (younger), you chose what age difference is acceptable to yourself. People might 'borrow' your youth, but they can't take it away from you. Spend it wisely.