I'm still wrapping my head around all the information, but getting there slowly. Being a healthcare professional helps, but it's still a pretty good learning curve, because sleep medicine is most definitely not in my wheelhouse. But maybe that knowledge will help someone else here. If you're new to this and feeling dumb or inadequate because it's taking time to figure things out - don't feel dumb or inadequate. There's so much information available that it's not a field of study you can master in a few months.
Anyway, my employer put us on a high-deductible health plan after Affordable Care Act became law, so I'm "enjoying" the freedom to buy whatever mask I want and experiment. Fortunately, the online DME I'm using offers 30 day returns on masks, so I've only spent a small fortune instead of a large one. I'm completely embarrassed to admit how many different masks I've tried in 2 months (LOL), but right now I'm using a Dreamwisp, and it's the closest thing to a good fit for me that I've tried. I haven't dived into full face masks yet, mainly because I'm a side/stomach sleeper and a little active (although apparently not as active as before CPAP, according to my wife). The two most comfortable masks I've tried were the Sleepweaver Advance and the Airfit P10. The Sleepweaver was a dream come true for 2 nights, then started leaking into my eyes no matter what I did. The Airfit would be perfect if the headgear was about 3 inches longer so that I had some room to adjust it to fit. I can't put the clips on or it's way too tight, and adjusting the two halves of the strap makes it either too tight or leaky.
The Dreamwisp is not quite as comfortable, mainly because I'm super hot-natured, and it makes my nose sweat.

I have downloaded both Sleepyhead and Res-whatever since I'm using a ResMed. Wasn't 100% sure I needed both, but as we say in the guitar world, why have 1 when 12 will do? Unfortunately, I don't have an SD card reader on my laptop, so I've had to order one of those. According to the clinician readout on the Airsense screen when I'm in clinician mode, I'm having <1 AHI average per night for the last 2 weeks, no central apneas at all. My mask leak is all over the place but I'm not sure if it's mouth leak (don't think so because my mouth isn't nearly as dry when I wake up now as it was pre-CPAP), true mask leak, or just aberrations because I'm pulling the mask away from my nose to wipe, scratch, etc. My overall leak numbers have been below 20l/min the last 2 nights, though.
So now to an actual question. How long do you give a mask before you decide that it's not the answer and move to the next one? I've been anywhere from a week to 2 hours. If I can't make it seal, I'm not wasting a night trying to sleep in a wind tunnel. Other than that, I've tried to give each mask a fair trial, while staying in my return window for my DME.
I'd love to hear from everyone else, though. How long do you trial a mask before you move on?