How long can I afford to being away?

I'll try to not exaggerate or under exaggerate, but basically:
A girl, best friend, we've been in a relationship but ended it because we both found the pressure of keeping the relationship difficult, and preferred just to be friends, and I like it that way, even though we share the feelings for each other. I don't want to lose her at all...
I've not talked to her since Monday, because of exams... And I did this to be able to focus on my own things for a few days. But how long can I go on without risking her losing interest in me? Even if we're just friends? How long until she won't feel about me the same way? Another thing is I miss her a lot, but I've been having a quiet phase for a few days and I feel as if it will be difficult to suddenly spend all my time with her as we did previously... Oh god this probably sounds like a mess, I think I'm ranting,

Summary: How long does it take for someone to lose feelings for someone else after "x" number of days not talking to them? And is it better to not talk at all or talk a little until the exams are over (which I worry about more since they may think I don't care about them that much... which makes no sense at all)...?

sorry for the mess!

There's no set amount of time, sadly. It'll differ from person to person.

Also, don't try to 'be friends' after breaking up. It doesn't work. You might think that you're over her or you can set aside these feelings for her whilst being friends so that you can keep in contact with her or keep her interested.. but it'll probably end up being a big mess. Even talking just a bit can be bad.

But anyway, if you want to be friends you both need to be over eachother, and that doesn't happen quickly.

It's a strange situation because, we love eachother, but somehow we felt so much more uncomfortable when in the relationship... So I guess right now it's like being in an unofficial relationship? It also gives us the freedom to just be ourselves a little more I guess?
And the good news is I'm back talking to them again ^-^ First few hours were a little awkward but I think we're back to our crazy selves again D So thank you