Interesting direction the thread has taken.
I find that policies vary widely. I find there to be value in maintaining a good relationship with a small shop. I have never had problems getting fills when I need them, but I can appreciate that the situation can be awkward in areas where there is little choice of dive shops.
Some of us live in small apartments and condos with no place for a compressor. I just love it when people say “get a compressor.” Living small allows lots of disposable income for diving.
There are many ways to deal with air logistics in remote areas or in other situations where it is expensive or time consuming to get a fill.
* You can have many cylinders. I have around 20. Typically I get 15 fills at a time, and can plan to get fills at a time that works for me and from a shop that I trust.
* You can obtain air in K or T size industrial 4500 PSI or 6000 PSI cylinders and fill your dive cylinders from them. Not common but there are situations where it works particularly if you have friends at a location that gets regular deliveries of other industrial gasses. You maintain a cascade with the Ks or Ts, fill your dive cylinders when you want, and have the industrial gas guy swap empties.
* A variation on that is that you can get a cascade trailer.
* You can use a portable compressor for fills at or near the dive site, i.e. in the parking lot.
* If you have a boat, you can use a portable compressor on your boat, or install one permanently below decks.
* You can form a club, formal or informal. It is not unusual for 2-4 people to purchase a compressor together and keep it in one member's garage or small business. Larger groups can sometimes find free space with 3 phase power especially if there is a public safety or other charitable aspect of the group's mission.
* There are still people who manage to get fills at a firehouse. Firehouses often have dive teams and therefore pump Grade E