Elevator modernizations

I think all depends on how frequent are the breakdowns and what the reasons are. Our elevator consultant told us 20-25 years and I know they are incentivized to replace to create work for themselves and their elevator installer friends.

What companies are the most reliable for this sort of thing?

Quality of work or price? On the latter, you get screwed as it is union job and they want to make a lot of money.

There have been changes to elevator code that could get quite pricey for some buildings. Door lock monitoring by Jan 2020 and secondary emergency breaking by 2027.
Elevators installed or refurbished since 2009 are likely compliant.
I think the door lock monitoring is only in the $5k to $10k range but the secondary breaking one will be quite painful.

For the quality of work...we have been recommended Champion Elevators so far.