Apologies if this has been covered somewhere I missed.
As an experiment, my DM has asked me to rebuild my 5th level Warlock under 5e rules. The biggest issues I've run into (besides the lack of an undead patron) is selecting spells. The spell list for Advanced is limited enough that it...
What I love about this design is that it incentivizes your adventurer to never fully retire--after all, as long as you keep killing a few CR worth of creatures a year, you can keep looking young and extending your lifespan. Perfect for a less-than-ethical warlock.