going without running pump while on vacation

[JohnT]

Before I had a timer, I just had the neighbor who feeds the dog turn it on one day, then turn it off the next and so on. Not optimum, but it works.

[matt4x4]

I would not leave the pool off for more than 3 days (with a high Chlorine concentration to start).
My recommendation is:
If you can't get someone to come by and check it, then keep using your extension cord, plug it into an outdoor timer, plug that into a GFCI outlet, set the timer between 6-8 hours a day and leave it be, if something gets wet and shorts, the GFCI will take care of it, otherwise, your pump should run for teh preset time every day (barring a power failure).
If you use a digital timer, a power failure will render it useless until you reprogram, a manual one will keep working - cycle may happen at different time, but it will at least cycle the pool.