Currently it seems that the "Estimated" time is calculated as an average based off all past builds (this is just my guess based off the estimates for several projects). If my understanding of how this is arrived at is correct, calculating it based off the last 5 (or 10) builds would be more accurate. This solves two issue that I can see:
1. I am working on a project that took a lot of failed builds to get the deploy process correct. This resulted in an estimated time of 25 seconds, even though a successful build takes 10-11 minutes.
2. As projects expand and builds become longer, the estimated time will be slow to reflect this.