I'd recommend sticking to 250 to 300, maybe 500 recording per disk, at this time.
For shorter show, this means you could get by with a smaller disk.
Figure less than 2000MB/hr for HD, 1000MB/hr for SD and 4000MB/hr, perhaps 6000 for OTA MPEG2 full channel.
So a 500MB disk may be the maximum desirable for 1/2 hour shows from Dish for a filing an EHD.
Which is more important in determining the limit, MB or number of shows, or number of titles?
-Ken