Powering COB LED with "under-voltage" LED driver
Yes it can be run for a long time as long as the temperature of the LED stays within operating temperature.  A CoB drawing 1.5 Amp needs to have serious thermal management.

If the LED gets so hot it will burn you instantly or if water sizzles on it, it is too hot.  Keep its temperature below 100°C. 

At minimum you will need a heatsink and very likely a fan. IF no fan the heatsink is going to have to be big.  

This CoB can take 2.7 Amp so you are in good shape that way.  

This supply has 88% efficiency. 

36v x 1.5A = 54 Watts 

54W / 0.88 = 61.63 Watts.  Near Perfect, Running exactly as expected. 

It should be the job of the power supply to limit the power to 50 Watts if necessary.  You are driving the supply 20% over its rated capacity.

I would be concerned if the power supply gets too warm. It should not get too hot to hold in your hand.