Bicycle Mechanics - chain and cassette replacement question

As part of regular preventative care...

Do you prefer to change your chain frequently (once a year) to prevent, as much as possible, wear to the cassette?

Or... do you prefer to just give good care (cleaning, lub) to both and let them wear together and replace them both at the same time?

I've heard opinions for both.

It is overly conservative to change both, as typically a cassette will last for 2.5 chains and chainwheels for 3 to 4 chains, depending on your usage. On many triples
for example the small CW is only used a few % of the time and might last 2-3x as
long as the middle or large CW. The higher the # of speeds on the cassette, the shorter the chain life. Recent reviews suggest that 10spds may have only 40-60%
of the life of 9spd chains, so the cassette may out last even more chains. My experience on my bent which has both 8 and 9spd chains is that the 8spd chain lasts 8-10k mi where the 9spd chain lasts 3-4k mi. I refer to road usage, ATB that is really AT is a whole nother experience. Steve.

Another roadie here. I clean and relube my chain fairly often, maybe every few weeks or after I've ridden in the rain, and change it when it has lengthened 1/16" in 12 link pairs. I probably get 3000 - 3500 miles per chain. Consequently, I rarely have to change cassettes. Running a worn chain also speeds chainring wear. It's just lots less expensive to buy one of those on-the-bike chain cleaners and use it often.