Depending on how many files you're dwnlding at the one time, then yes the dwnld rates can very as one gets more share than another & then swaps back. It also very much depends upon your sources. Either how much upld bandwidth they have available or are willing to share. Some T1/T3 sources only offer a miserly upld speed. Also they may be sharing their bandwidth b/w several users. Best if you can dwnld from moer than one source.

Some hints: A well set-up LW can start to automatically continue its dwnlding after it's settled down perhaps 2 out of 3 times you open LW. Optimising LW & Maximising Uplds & Dwnlds A (1st post only) & also see RaaF's link above & last & least are search & dwnld hints. The latter one I've been thinking about re-writing for some time. That's just for playing it safe. eg- I show all speeds & qualities.