Hello Ellery,
Do LALR parsers care about arbitrary lookahead? LL(k) parsers do.
LALR needs to be able to unambiguously determine all the /completed/ productions to the left of each point by looking at nothing beyond the next token to the right. This might not be conservative enough, but I seem to remember that most parser corner cases don't crop up in practice.
In general LL needs to known exactly what productions are "in process" where are LR needs to, at each level, have a finite set of options and only needs things to become unambiguous before it finishes a production.
(BTW I'm taking (but haven't yet finished) a compilers class so I might be missing something)
