I need to pump air in my tires about every 1.5 months. Someone told me this is too often.
How often did everyone put air in their OEM tires?
You don't say where you live; with Winter coming on in the US, perhaps it's just a normal decrease in pressure with lower temperatures?
e.g. 36 PSI set at 20°C will decline to 32 PSI at -10°C
I last had to pump my tyres when it was less than 10°C (Travelling in Southern Australia), and 4 months later, it's 30°C (Northern Australia), and I haven't had to add any air, so the hotter climate is compensating for any minor leaks.