Which current can a multimeter measure for an indefinite duration?
Here's an approximation.  The answer is probably too low.

30 sec every 15 min is a 1/30 duty cycle.  So assume 10A dissipates 30 times what the meter can handle continuously.

Power dissipated in a resistor is proportional to current squared.

So we would get the same average power with a current of 10 (1 / √30) amps = 1.8A