Long story short, my job pays me $600/month car allowance. I cover gas and maintenance but my personal car area of territory is dense and geographically small and I'm not doing 8 hours of fieldwork 5 days a week either so it's not crazy miles.
I have 2012 Civic Si with 120k miles on it. Love the car, not great to spend a day in doing calls and getting up there in mileage and going to need some cash infusions soon.
I am considering either replacing it with another enthusiast type of car but newer and nicer before it reaches the age where it starts getting unplanned downtime frequently.
Other scenario is, retiring it as my commuting vehicle and keeping it around as a paid off part time ride and buying a cheap ish appliance car to shuttle my T shirts and customers around in and using that for business purposes. I'd pay off the Civic and the car allowance would cover my work car. I also own a 1998 4runner so at that point I would own 3 cars and I rent. While this would be workable it could be annoying to deal with parking.
Right now the extra car allowance is just going towards paying off my civic early.