Doing the original search again for the files has always been more effective than the Resume functions. But yes, that is somewhat time-consuming in itself. And unfortunately LW does not save searches between sessions unlike some other clients.

LW 4 and 5 will periodically attempt to reconnect to previous hosts for each incomplete download. I cannot remember how frequently, either once every 30 or 60 minutes. But LW will only check their previous known host addresses whom had the file. Whereas these persons may have highly dynamic ip addresses and in the meantime their ip addresses have changed. That's why doing your own search is better than either the resume function or leaving it up to LW to start them by itself.

LW will go into semi-sleep or inactive mode if it has not been actively used by the user after a period of time. This means it drops a couple of ultrapeers. This should not affect downloads. Since searches are not being done the extra ultrapeers are not needed and lets them go so other persons can utilise them. I don't think this mode is called sleep, but I cannot remember the word for it.

If a file stops downloading at a certain percentage, then either LW has lost connection with the host, or the host has gone offline or maybe that person only has that much percentage and is themselves still downloading the file (Thus you were downloading the file via partial file sharing.) I find I simply lose connection with the host sometimes when downloading. I do not think this is an uncommon happening. I see it quite often in my upload window dare I say it. If LW is unable to reconnect to the host then again, I recommend to re-search to see if you can get back into that host's queue or else, find other hosts with same file (if anybody else has same file.)

Ultrapeers will occasionally drop leafs or other peers and pick up new ones. This means a couple of things. One it can make it harder to relocate the host if you lose connection, secondly, fresh searches may find new hosts with same file due to exploring different part of the network. Keeping in mind also that hosts come and go from the network all the time.

Not sure if that's of any help.