Month and a half is nothing. Takes more on the order of like a year or more for gas to go bad. When it does it's nasty. All ya gotta do is take a wiff and it'll make you want to puke. If it goes REALLY long and bad, it'll actually turn into a gelatinous goo. I had my stang up on jacks for 2 years with a full tank of gas. I had dumped some fuel stabilizer in it when I parked it, but 2 yrs is 2 yrs. When I went to revive it, started right up. Only real thing to watch for on something that sits a lot is varnish buildup in the fuel system, especially if it's carbed. But that is a drawn out, over time sorta thing.