High thermal load PCB for short duration
60W x 30 seconds = 1800 joules

That spread over 10 minutes would be an average dissipation of 3W for a rather large board.

If things are not overheating in those 30 seconds you should be fine. Otherwise a heatsink to dump that energy into can help make thigs easier.

How much heatsink? Well to raise a metal a temperature is joules per gram per degree c. For aluminium this is 0.9, so lets say you want the heatsink to not heat more than 40 degrees above ambient for the pulse. 

1800  joules  / 0.9 / 40 degrees = atleast 50 grams of aluminium. 

This does not quite tell you how quickly the heatsinks temperature can dissipate that energy. So it will probably be slightly warmer on subsiquent pulses. But you do not need much metal to absorb thr worst part of the pulse.