I've decided to go back through LPI / LPII / LPIII and remove the majority of the time limits (since these packs predate the infinite time option, and I never bothered before now to update them to conform to the modern standard of generally not using limits).
Lemmings Plus I is done. All levels have their time limits removed, except the following (which have the same time limits they always had):
Mild 26 "No Salvation I"
Wimpy 7 "No Salvation II"
Wimpy 22 "Fast enough?"
Medi 13 "No Salvation III"
Medi 23 "This is..."
Medi 30 "Consider Everything..."
Danger 2 "Metal Lands"
Danger 6 "Alternative Logic"
Danger 11 "The Warp Room"
Danger 16 "Grounded!"
Danger 17 "Perfectionism"
Danger 18 "The Buildo Station"
Danger 20 "No Salvation IV"
Danger 21 "It's The Latest Craze!"
Danger 24 "Find A Way Out!"
Danger 29 "Pipeline Problem"
PSYCHO 2 "The Parking Lot"
PSYCHO 3 "Express Lane"
PSYCHO 4 "Think Outside The Square!"
PSYCHO 7 "Turn Back With Care"
PSYCHO 13 "Go High Go Low"
PSYCHO 16 "Crosswork"
PSYCHO 20 "No Time To Die"
PSYCHO 25 "Bullet Lemming"
PSYCHO 27 "No Time To Die (Part 2)"
PSYCHO 29 "No Salvation V"
Similar updates to LPII and LPIII won't be far away.