Waiting for marriage?

Backstory: I'm 18 and my boyfriend is the first guy I've dated. We're coming up on 2.5 years together. When we started dating, it was very important to me that we wait until marriage and he has always been very mindful and respectful of that, never pressuring me to do anything physical. All we've done physically is lot of making out and a little bit of dry humping recently.

I'm not really religious anymore but I still want my husband to be the only person I have sex with. My boyfriend and I have spent the past year knowing that we'd like to get married as soon as the period of long-distance is over. However, that's in four and a half years, and he's already been patient for this long. Should I just let our relationship get more physical? Is there any real reason to wait if I know he's the one I'll marry? I'd really like some insight from people who DID wait for marriage or who, like me, intended to but changed their mind after being together for a long time.