Doesn't cost any more to keep the tank as full as possible - just "costs it sooner".
Moisture in the tank (which, if excessive, eventually will find its way into the lines) is always problematic, especially in freezing temperatures - nothing like a "no-start" due to frozen lines to mess up your day - especially if it takes days to thaw - always use gas line de-icer in winter - maybe not you guys down south, but anywhere you get snow - also, it's hard on the pump if it running and nothing is going through.
Change the fuel filter regularly - any obstructions/constrictions means the pump is working harder than it should and will burn out quicker.
In cases of what looks like pump failure, check the underhood relay (I've had issues with this one), the fuel cut-off switch/inertial switch, wiring and connectors (especially the main connector on the underside of the truck, under the driver's side/seat, kind of next to the transfer case on a 4x4 - 4x2 same place, just no transfer case) for corrosion - that's a show stopper for sure.
Fuel pumps are funny - can last the life of the vehicle or just go after so many miles - good for you to keep your eye on it, but no guarantee that because it failed before at that mileage that it will again.
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P.S. Keep your membership in CAA (AAA in the States) current in case you need a tow in case it does fail despite everything