That's a big boy! Looking good. I've never grown a type that large, but a month on the vine sounds like enough, or getting there fast. My guess would be that if the coloring looks like it does on the seed packet, you're done. I've left pumpkins on the vine too long and they got a rotten spot on the bottom where it was touching the ground, so that's a risk.

If anybody else here advises you to leave it longer, I'd add that repositioning it could be a good idea, maybe get some sun on the opposite side if you can.

Keep turning it like sunny said or I have put them on a couple of bricks just keep it off the ground now. ...I find when the vines start to die going to the pumpkin it probably close... this also applies to cantaloupe and some vine squash. Watch over watering it, can cause rot or splitting. Looking good