The answer to your question of how long it takes to get used to the wacky fluty explorer sounds, will depend on what machine(s) you used, before moving on/up to the Explorers. If you are new to md'ing (and thus not biased to accustomed to certain patterns, sounds, swings, etc...) then I suppose the learning process would be quicker. But if you're used to machines that had a fast swing (xlt, spectrum, 6000, and any other such machines), then perhaps you'd hate it for a long time. Also if you're coming from a machine that had a monotone (or *nearly* monotone, with only 6 or 7 tone-quadrants), then you might also have a longer learning curve.
Before I switched over to the explorer (from Whites Eagle SLII), I was hunting a park with an explorer fellow, who was effortlessly pulling silver and wheaties from beyond what ....... I had to be honest .... my Whites could get. I tried all different settings, re-balancing right next to flagged signals, etc.... Eventually I had to realize that this new beast (the first I had seen of it in any CA turf) was truly going deeper, and with better ID. So I ran out and got one. IMMEDIATELY I hated it, and couldn't figure it out. Everything sounded the same: Like a flock of sick geese. So I made an appointment to meet up with this other hunter again, at this same park. He flagged a few signals that he was saying were going to likely be deep wheaties or silver. Each time, I'd listen in to what he was hearing, watch the way he swung, listen to what he was trying to isolate, etc.... Conversely, if I flagged something, he'd check it, and give me an analysis. Eg.: "nah, corroded zinc at 4" or "nah pulltab" or "nah, nail false", etc... WITHIN 15 minutes the "lights went on" and it made perfect sense.
So the best way to get used to the explorer is to hook up with a proficient user, and see what he's listening for. Either that, or force yourself to dig 1000 signals

Make sure it's a place where there will be some deep oldies (ie.: NOT a hard-hammered park that not even the pro's can get stuff out of anymore). Because if you go to only sad sorry places with no classic 4-star deepies, then your mind will never get the chance to have side-by-side signals to compare to.