There is not much we can do about it because even when we have 5000 XMR it gets sold within an hour or two. There are some people that are monitoring our XMR balance with scripts via API to receive notifications when it's up then come and buy it all. However this problem (which is not really a problem) will get some workarounds eventually.
Is it possible that some big centralized exchanges are buying from eXch?
I won't be surprised if that was the case, but I noticed other coins can also dry out sometimes , for example there is not a lot of Bitcoin at the moment
(a bit more than 0.92 BTC).
At least we can see balance of reserves, that is impossible with big exchanges, so it appears like they always have them even if they don't.
Also, it's possible to backorder XMR on eXch. What some of our users do while no XMR reserves are available is creating and funding an order so it gets executed in a first place when XMR reserves reappear with sufficient balance to cover their order.
Sounds good.