I use open tunings a lot. They definitely do fatigue the strings, but it's the price you have to pay, I guess. If you use open tunings often, you'll have to change strings more frequently.

Regarding "string memory": yes, it exists. A helpful hint is to always make sure you tune UP to pitch, not down. If you need to tune a string down (low E down to D, for example), first tune it below the pitch you're going for, then tune up to pitch. This can help overcome string memory, and keep you more firmly on pitch for the duration of the tune.

Standard tuning does have some advantages over open tunings. For one, it's "keyless"; it doesn't steer you to a particular key, but is equally adaptable to a lot of different keys. For another thing, the intervals between strings are pretty uniform (with that one exception between the second and third strings), so it is easier to find your way to the next note in the heat of the moment. The final advantage is that it IS standard -- so again, it helps you become, and remain, more familiar with the fretboard, allowing you to veer off in any direction you choose with some confidence that you'll be able to find your way.

For all that, however, I like open/altered tunings. I see no reason not to enjoy them.