You can lose more than a pressure gauge, if we get a really cold winter again. The risk depends on your pool's layout, however.

The killer combo is an ice storm that takes your power, followed by temps that go below 20 for several days. You MUST run your pump if you don't close.

Regardless, you want to get your algae all gone before you close, and you want to get your chemistry 'right' given that you have a concrete pool. You probably should post a full set of readings on BOTH your pool water and your tap water (FC, CC, pH, TA, CH, CYA . . . on pool only)