I have a 211 installed now and without the EHD the EPG on goes out 2 days - Sunday 6-12-11. With the EHD, I get the extended EPG.
Are you sure? Guide loading speed is one of the major complaints about DIRECTV's DVRs. It can take upwards of 24 hours to fully populate the guide and for whatever reason, they still have that mysterious 50 Series Link limit with one of the the slowest responding guide grids extant.
I've found that even with a 7 day guide, the information can change quite a bit before a program schedule actually airs.
As I said, my 211 had the extended epg as long as I have had it. I got it at the same time I got my original 722.. There was no difference when I added the ehd.