If you come into a LDS on Thursday or Friday night or on Saturday morning it could be a bit of a wait. We can fill 4 tanks at a time and can control the fill rate of each individually so it shouldn't be too bad but, you're right spark, Friday night in July can be crazy.
Most LDS including us don't like tanks left for fills. Strictly speaking they must be tagged for service since they are our responsibility while in the store. More than once a customer has left a tank and then not picked it up for several days or even weeks!! When one goes missing (not tagged!) it's a real problem. The owner has no tag, we have no tank - who's at fault? We should have tagged it and given him a service number. Without that we have no responsibility but... at our store I hate to disappoint anyone so I've actually given the customer a new tank based on his word that he did bring it in AND didn't already pick it up. Now you see why we don't want tanks left for fills. The same applies at other stores. If you leave the tank, be certain to get a receipt. The store does not have to give you anything without one.
Ther answer is to bring your tank in during the slower periods. Weekdays anytime, Thurs, Fri, Sat or Sun midday. It may not be the most convenient but I suppose it not a lot different that lining up at a ski lift or golf course on a Saturday morning. For sure it's not fair to blame the owner of the LDS.
Let me suggest that most tanks coming in for fills are at 1000 psi or more. Therefore losing 200 to 300 psi from a regular fill is really more a problem in the divers mind than in practice. However, I too would be irritated if I thought I was paying for 3000 psi and didn't get it. Maybe a change of thought is in order. As I said earlier, you're not paying for the air in the tanks - you're paying for the compression and delivery of the air. Since 2500 is as good as 3000 for most dives, reguler fills are not as big a deal as they're made out to be. If you can accept that idea great. If not and you insist on 3000 psi, you may have to line up.
We get very few divers complaining about the time needed to get a good fill. Perhaps because we don't charge for air fills and also the pro shop is interesting.