Hi Mark,
I think it's mostly been summarised already but, in my view, very rarely will a carpet be "dry" in 30 mins. Drying time is an issue for customers only because of horror stories and as doc carpet says most customers are more than happy to hear a dry time of 4/5 hours or half a day. I don't think its the big issue we think it is. Most savvy customers want the carpet cleaned as thoroughly as possible not dry as quick as possible! And of course actual dry time will vary wildly according to fibre density, ambient temperature etc, etc.
One tip I would suggest - don't get to hung up on technicalities. Customers are generally more interested in benefits not features - two different things.
Good luck!