How quickly can you know a partner?

[Bathbedandbeyond]

I’m 8 months in and there have been no red flags.

He is calm, kind, considerate and I’ve met his family and friends (met through mutual friend, she adores him), who all think he’s great.

He has a good job, very responsible and requires a DBS check.

He does have a string on failed relationships though. He (my friend) says he never found the right person. I know that he’s told his guy friends via group message that he’s finally found what he’s been looking for in me (one of his friends sent a screen shot to our mutual friend with the caption ‘at last’)

AIBU to think that I’m seeing the real him or is he going to leave me a heartbroken mess

There's no guarantees but I knew dp was the one for me after a couple of dates, he says before we met in real life he knew. So things progressed very fast but why hang about, not getting any younger

You don't really know someone until you get to see how they behave when things are not going well. It's easy to be calm, kind and considerate when you are under no stress or pressure.

It's when are tough that you really get to know someone.

When I said 'test' I don't mean I'd set up scenarios to test them, (that would be weird) but that I would pay attention to how they react over certain situations and these would be deal breakers. I think that it's healthy to have standards in a relationship. In the past I didn't and was treated badly. When I raised my standards I ended up with DH who is good and kind and trustworthy.

Oh, standards absolutely.
Know your "hard limits" and stick to them.

You are both individuals and equals. Neither of you is each others parents.

You have to find a balance that works for you both. And if one has to make more sacrifices than the other, is it really worth it?, From experience, not a chance. One person gets "shafted" sooner or later.