Until you don't.
Vanquishing can get hella exhausting, especially when the dragons continue to breathe fire in your face and the flying monkeys are hurling banana peels and feces at you from the sky. You can see that clearly (since those pesky eyelashes were singed off your face) the two of you are not meant to be together. However, you still love them and feces withstanding, you still actually like them. You can't imagine your life without them but you know you can't continue on in this vein. It so obvious; you were created to love each other, but just as friends! Duh!
Au contraire mon frere (or sister). Can you really be friends with someone who's seen your O face?
Some say yes, some say no. I say yes, with an asterisk. Yes*. But first, let's define what we mean by friends. Here are the categories:
Level 1 - when you accidentally run into each other, you exchange hugs, ask if that cousin ever finished law school, "tell your mama I said hello" and keep it pushing.
Level 2 - holiday/birthday phone calls, when you accidentally run into each other, you exchange hugs, ask if that cousin ever finished law school, "tell your mama I said hello", talk about getting together sometime for coffee/salad/licorice but neither of you actually make it happen.
Level 3 - regular communication, hanging out together intentionally, making time for them, etc. You know, how you are with your other friends.
Hopefully, the breakup isn't so ugly that level 1 is unachievable. However, with levels 2 and 3, I am asterisking all over that. Here are the conditions under which true friendship can potentially be achieved:
*1. No sex. (See, y'all aren't really friends.)
*2. If either of you are in a relationship, the new boo knows that y'all have seen each other naked and is okay with your friendship.
*3. There has been enough time between the breakup and the burgeoning friendship.
*4. Your expectations of this friendship are no different from your other platonic ones.
*5. Your interactions within this friendship are no different from your other platonic ones.
*6. The friendship does not hold you back from dating others.
*7. You aren't rehashing or punishing each other for what went wrong in your relationship.
*8. One of you isn't still in love with the other.
*9. Mercury is in retrograde.
Often, we move into the "friend" space too quickly after a breakup. Being friends feels much better than not having the other person in your life at all. However, if we are really honest with ourselves, it's how we rationalize holding on to someone when we don't want to let them go, even if we want to let go of the relationship. The hardest part is giving ourselves enough of a break; 2 weeks is not long enough. I don't have a specific time range, as it is dependent on how long the relationship lasted and how much fire and feces was dealt with. For some, it could be years before you can actually be friends, while for others, 3-6 months is all they need. You may also find that if you wait long enough, the desire to be friends may pass.
There's can also be a level of intimacy in your friendship with an ex that you don't have with your platonic friends. While it can be satisfying to have someone in your life who knows you so well, it can prevent you from moving on to someone else, as your intimacy needs may be getting met in this friendship. That is why it is not advisable to carry on a sexual relationship with an ex friend because it's the sex that helps differentiate a romantic relationship from a platonic relationship.
So can you be friends with your ex? Maybe...but make sure mercury is in retrograde.