I'm expecting to charge my Model 3 less often than once per week... but obviously it depends how often you need to charge. As long as both of your cars can handle 2 days of normal use on one charge, plus a bit of a buffer so you aren't running to 0, you should be absolutely fine.
So if your commute is 50 miles, you need a car that has about 250 miles claimed range (2 days of 100 miles round trip, which would take you from 90% to 10% charge). As your battery degrades a little, you can eat a little into the 10% buffer (you probably don't need to get home with 25 miles of range)
Repeat that calculation for your second car too, and as long as both can handle it you're good to go. The simple calculation is to look for a car with a real-world winter range that is 5x your commute distance, or 5.5 if you want to account for more degradation long term.
So as a recent example for me (before I moved jobs), we would have needed 1x 200 mile range car for my 40 mile commute, and 1x 30 mile range car for the missus. We'd probably aim for more like 100 miles on the second car so that we can use it in the evening to go shopping or nip around town too, or so that we could use it for the longer commute in an emergency - so you can factor in some convenience, particularly on the cheaper, shorter range car.
