Can you wake up and smell the hypocracy?

When my husband and I separated, I started dating someone. I was 26 and he was 40. (Not as extreme as yours, but nonetheless.) He was pretty energetic as well and, like you, I am not the partying type and usually am OK with just sitting in the home and just spending time together. After 6 months, I started to see a pattern... even though he was energetic, he needed to take naps and started being too comfortable just sitting at home. Obviously, I don't know your boyfriend, but your stepmother might have legitimate claims and reasons. But, regardless, I hope you're happy!

I don't think it's hypocrisy at all.

She's trying to give you the benefit of her experience. She probably believed the same things as you ten years ago but has since seen the reality of the age difference. I think she may have been skating around the main subject of discord between couples like yours - sex.

As men get older (and it doesn't matter how well they look after themselves) they find that getting an erection for a second round of sex takes longer and longer. Some may find it increasingly difficult yo get an erection at all. I'm not saying your bf is on the brink of this but imagine when you're in your early 40s and raring to go and he has to take a pill to get a decent erection and then wait for it to have an effect ... It's not always easy.

Another common cause of discord occurs when the woman decides she wants a baby and her partner refuses to even consider it at his age. He's been there, done that ...

Just keep in mind that many older men just want companionship. So over time are you willing to just have a simple relationship possibly without sex? I know that doesn't happen to all older men but it does for many. I'm in my 50's and dread going out with men my age. They think walking around the mall is "fun" and as for intimacy, they want to just hold me. YUK. Even if your man is fine now, odds are age will take away his fun stuff soon. Many older guys just want young women to make themselves feel young again. Sad.

Your stepmother is 33 and your father is 49.
You are 27 and your bf is 50.
Is your stepmother indirectly complaining about her marriage?

Maybe she is talking from experience. So, it might be worth listening to.

she might be trying to be helpful because there have been down sides to her marriage with her age difference and yours is even more. I'm pretty sure she's just looking out for you as one women to another, not really stepmother and daughter.

Just take what she says as her opinion.  Either use it or toss it.

If him being a old man does not bother you go on with the relationship? Is he ok with having kids at his age? He must be a good looking and young looking 50.

Just hope that you are not his mid-life crisis. Watch out that he doesn't try to controll you. Be careful of this relationship. I was married to a man more than 20 years my senior and he was very nice at first. After we said "I do.", he started chasing other younger women and he became abusive when I asked him to stop.
I knew 2 other women that were involved with older men and the men were very controlling.
I know not all situations are the same, but please careful. Wish you happiness.