A lot depends on the vendor, if they are a large vendor shipping hundreds of packages then they probably get inundated with hundreds of messages too so you may be looking a 2,3 or 4 day wait for a reply. My advise would to be to carefully read the vendors page and any links they may have to their FAQ, terms and conditions etc as often you can find the answers you seek without having to send a message at all. I know vendors do get pissed off with being asked the same things that are already printed in plain site, I'm not saying that is what is happening in your case, I'm just making you aware often the majority of questions buyers have are well covered on the vendor page. As a general rule though I like to make nice with a vendor before I buy for the first time though and a few pm's to see how they respond gives a reasonable indication of their response times etc, if I do not get a response I usually go and shop elsewhere with a more receptive vendor, but that's just me. Hope that helps.