Should I self-impose a word limit for a journal article abstract The author guidelines for the Journal of Computational Physics do not specify a word limit for the abstract, saying only that it should be 'brief'.  But should I impose a word limit myself?  I have heard that some indexing services can truncate overly-long abstracts, though I've not come across evidence that this is this case.
Yes, you should limit yourself because the goal of the abstract is to be short.
Now, where to put the limit?

A good idea would be to look at recently published articles in this journal and note their length.