Do you think its ever to late to talk to someone from your past?

To late?  I'm not sure what you mean by "is it too late".  I don't see any reason for not "talking" to someone you've been in a relationship with (in your past) .. If THAT is what you mean.  Of course much depends on just how the previous relationship ended but it's nice to be able to remain cordial friends even after a relationship.

THAT is what grownups do.

I guess that would depend on how the relationship / friendship ended. If it ended badly, you might consider why you want to re-connect with someone. If you behaved badly and you want to make amends, you might want to say so when you get back in touch. If you and the other person just drifted apart, and there weren't any bad feelings as a result, give it a try. The worst thing is that they say no.