Terrible idea to not disclose your age. Do you assume he will never find out?! If you go on holiday together, and he takes a peep at your passport, he will see you true age. He will not appreciate being lied to. A 3.5 year age gap is nothing, but lying about it is a big deal. (Even lying by omission.)
I know a woman right now who is 57 and is dating a man of 52. She has told him she is 48! 3 months they've been dating, and he is now going on about a weekend away in December, and she's terrified he will find out her age. I said 'of course he will. You should have told him the truth straight away,' but she said 'he wouldn't have been interested if he knew I was 5 years older than him!' (They met online!) The more time goes on the worse it will be when he does find out!
I also remember a thread on here several years ago, from a woman who was 42, and she met a man on an online dating agency too, and he said he was 48. Bit of an age gap but she was OK about is as he was good looking, and interesting, and was courteous and nice to her.
tl;dr, they went on seeing each other, and six months into the relationship she found out his real age.
61 😱
She was so mortified. He was old enough to be her father. She ended it immediately. She said she thought he looked/seemed a bit older, but some people do, my DH looks and presents as 5-6 years older than he is, and my next door neighbour's boyfriend is 31, 5 years younger than her, and he looks 21. However, even though she is 36, she looks 42-43, so he looks like her son, even though, the age gap is only 5 years!