It's overdue that I played this pack, as I don't think I've ever played completely through the Lemmix version of this pack.
Why are there time limits?

I personally find it quite hard making good levels where the terrain is already given, and I feel your levels reflect this sentiment in some places. Some of the levels seem a bit forced, e.g. there are 3 speed mining levels, or some are quite technical. So while being decent on average, I don't think this pack lives up to your other consistent top-notch quality levels, i.e. it lacks the consistency in being top-notch. But there are quite a bunch of neat levels in there, my clear favourite being 'Pick a Path' (I attached a variation showing what I initially thought I had to do, but that needs an extra miner). The levels I didn't solve during my first pass were appropriately enough named Struggle Street, (not so appropriately) Shady Diggings, and Hold Up. Especially the former two are also among my favourites, though when I solved the first one naturally the second one felt a lot easier when at first it seemed impossible. The last three levels were quite nifty too, though I've seen the last one as a variation in one of your Xmas packs already. 7 and 4 were neat, and 4-10 overall was a stretch of solid levels; I think the ones I wasn't very fond of were those where you had to repeat the same thing/trick many times.
Attached are all my replays...17 and 18 I couldn't be bothered to replay the level to work within the given time limits (as I just hope they'll get removed and then I automatically solved the levels

). Recorded some in 2015-08-09 and some in 2015-08-09-01; the older ones run in the newer version at least.