Putting two lights in a 60x60 worth it?

It depends. The ppfd, the lights footprint from the 150 watt LED lamp is (generally spesking not knowing the model of lamp) adequate for a 60 x60. As previously mentioned adding another light and raising the distance, this could cause a lot of heat, especially if these are the chinese made LED lamps which are basicly heaters with a light function. Some cold situations it can help though. What you could do is use the second lamp as side lighting, where it will actually make a difference. The general guide for side lighting is 1/3 of the overhead lighting, so 50 watt setting for side lighting on the second lamp. Its hard to imagine this being feasible in a 60 x 60 though, the space is really small and fire hazards, burning your plant risks will increase. I could be wrong though. If you are unhappy with your plants yield or potency there are better options in my opinion. Better genetics, the foundation of your grow. Adding C02 enrichment because plants love the gas of life and you can benefit from 600-1000 ppm. A bigger grow area. Increasing the size of the grow area is a goid option. A second 60 x 60 with 1 lamp each. Or think 100 x 100. You have to look at the manufacturer's recommendations for the lamps. Its good that you are thinking creatively, but the main thing is safety. If you try something new or unusual keep a goid watch. Just my thoughts on it. It could work just fine, I don't know. Not enough information to really evaluate your situation. Good luck, and I hope these tips give you something to daydream about.