I assume you mean standalone freezer, not refrigerator+freezer combo.
There is no reason to not use the lowest temperature setting, except the obvious wear of the machine.
The advantage of this is that food may keep a bit longer. The temperature within freezer is not uniform - it will be a bit warmer near the door. Depending on which location the manufacturer used for measuring, and inaccuracies of thermostat, it may vary slightly.
Many food I see has label saying something like -10C: two weeks, -18 C: until expiry date. So to be extra sure it never exceeds the -18 C, just dial in couple extra degrees.
Regarding the disadvantage of thaw times - use fridge and the built-in freezer it has.
The food you know you will be using soon - a week, a day - just keep it in fridge's freezer. It has higher temperature, so the food will not be as rock frozen. Whenever you use stuff from fridge, bring new ones from the freezer. I do that with ice cream - fresh from freezer, it can bend spoons, but in fridge freezer, its nice and soft.
In case you need to get something thawed out now - microwaves are great for that.
Alternatively, you can rearrange things in freezer slightly - move the stuff that you want absolutely rock solid frozen deep inside, and keep the stuff you want not-as-much-frozen near the door.