As long as the food in your freezer doesn't thaw I would think it would be alright. The freezer would have to work harder to return to the desired temperature setpoint once it was re-energized but I suppose there would probably be a net energy savings.

I have no clue if this constant up and down powering would reduce the life of your refrigerator.

I have been considering a similar idea. I was thinking about putting my fridge on a timer so it would only run once or twice during the night and letting it run all day when the sun is out. My refrigerator seems to be using about a constant 150 watts. During the day a couple of solar panels (and an inverter) should be able to power the fridge with no problem but having the fridge run all night would require more battery reserves than I am willing to pay for.

Does anyone have any experience doing this?