GPS Map 60C - Calculated ETA

[actomox]

Not so much a question as a gripe! Why does Garmin use such a stupid algorithm to calculate ETA?

You stop for 5 minutes for a coffee or to look at something of interest and the ETA goes back about 4 hours! As a result for most of the time the ETA quoted is hopelessly 'out'. I have noticed when I walk that, as the day progresses, the ETA gets progressively later - and I am sure I do not slow down that much in the afternoons.

Surely it would be more sensible to use a 'standard' kph for the remainder of the route for, say, the first elapsed hour and then use measured overall average or moving average speeds to calculate it for the remainder of the time. In car sat navs are MUCH better in this respect.

Anyone else have similar observations/feelings?