I think you should add shortest/longest length between updates along with the average.
Ex.
Product iPod
Recommendation: Don't Buy - Updates soon
Last Release September 12, 2006
Days Since Update 238 (Avg = 223; Longest = 296; Shortest = 154)
Ex.
Product iPod
Recommendation: Don't Buy - Updates soon
Last Release September 12, 2006
Days Since Update 238 (Avg = 223; Longest = 296; Shortest = 154)