To answer your question...yes...they can be heavier, lighter, closer or further apart. Even missed periods can be expected. I am 47.5

2 years ago, my periods started coming 24 days ...then this year, they were 28 again, like clockwork. This month, I missed my first period.
I think the rule is that once they become closer than 21 days regularly, you should talk to your gyn (at least that is what mine said).