I really have experienced very few 'failures' over the decades - the biggest problem, particularly in the past, being that getting replacement batteries for the cheapest 'cordless' ones was often impossible, so one could only carry on using them if one improvised some way of providing them with power (which I did in several cases).Of all the drills I've owned over the years I have no problem saying my corded Bosches (I have 3) have been by far the best, they are now 30 years old and I got the first and third in a Homebase end of line sale and the second in their summer sale. The pair of 18V cordles Bosches also from their end of line sale were the longest lasting and my favourites. I still have several B&D's (I think none with variable speed), wolf, corded drills from the 1980's and Makita from 00ies but none of them have maintained their good performance or reliability in the same way as the Bosches.
As for the corded ones, most, including the cheapest, seem to have gone on 'for ever'. I still have a number of B&D drills from 60s and 70s still working fine and a fair few Homebase power tools still going fine at 30+years. .... and similar for most of my 'workshop' tools, most of which were very cheap and remain in satisfactory service after 30+ years (saw tables, mitre saw, band saw, planer/thicknesser, morticer, router table, pillar drill, band/drum sander, grinder etc.).
Hand tools are, at least in my experience, a different kettle of fish, with very cheap ones tending to be pretty useless (and usually short-lived0!
