As you stated, there's nothing wrong with stretch goals, but for something that is a time-regimented achievement (requires X total turn-ins but you are only allowed to do Y per day) with this long of a stretch, yes, mudflation will gimp the reward by the time anyone gets it.

Having said that, I do expect that SE will improve the stats on this and similar items as new tiers are released, though we may need to remind them.