Actually read a similar post a while back, been able to purchase goods/services for the exchange of upvote, for that to be possible a price stabilization as you mentioned upward is needed, nobody would sell or render his/her service(s) only to find out that the value as dropped down considerably before the pay date.
And so many other possibilities out there
Maybe changing the time posts/comments take to payout into 3.5 days instead like the average time that displays the value of your SP and rewards right now could be something that would help these services.
Yes totally agree with that and the services could as well say, make upvote when the post is about to pay out, that way if there should be a drop in price, it won't affect the post/comment payout much