A check valve or hose inlet, depending on the position of the switch, might drain a battery down if you don't have a charging source when the boat is "left" unattended.

There isn't a "clean" answer for each boat and circumstance.

Float switches do fail, under sail (or even on a choppy mooring) you can cylce them when you don't need to.

The standard On-Auto-Off (Rule, for example) dedicated switch is a good idea in any case.

Locating the switch higher, will mitigate some concerns on short cycling -- but not the other concerns.

(HAVING SAID ALL THIS: I leave my bilge pump(s) on automatic. They are connected to the battery directly. HOWEVER, I leave the boat at a dock normally. Have separate engine- and generator-start batteries; and, 4 4-D AGM's for a house bank. On a prior boat, I had a bilge pump burn-out because the float switch was bad. It didn't cause a fire, the motor finally burned-up, internally. The case paint showed some distress. It was an epensive old, expensive PAR pump. It wasn't the pump's fault. It got replaced with a rule submersible, which get's cooled, to a certain extent by the water it's trying to pump.)