Carboy Size Time and Oxygen

I'm about to begin brewing my first batch at some point in the next couple weeks and have a question about my 6 gal Better-Bottle. My LHBS suggested I get the 6 gal to use as a primary fermenter to avoid using a blow-off tube. I'm planning to go from the primary to a keg. I want to be patient and leave it in the primary for a while, as some of you have suggested. I'm wondering though, if I leave a batch in the primary over an extended period, say a month, is there danger of oxygen damage after the fermentation has stopped with all that head space?

None at all. Whatever O2 isn't consumed by the yeast will be blown out of the carboy by all the CO2 that gets produced. You are golden.

You won't have any problems but I would get a blow off tube just in case. I use one for each batch.

Much obliged for the responses. One follow-up if I may. So removing the airlock and taking hydrometer readings won't reintroduce enough air to be concerned about?

Nope. Racking is the step you need to be careful about.

I'll second using a blow-off as well. I use a 6gal carboy and some of my latest fermentations have been so vigorous that I needed to use a blowoff tube for multiple days.

^^^^
Thirded. Headspace does not prevent blowouts. I've blown many a pint of foam out the top of a 6.5 gallon carboy.