See attached spreadsheet for a calculator to determine rough estimates for battery life for the Oyster Cellular.
Note the average time to GPS fix varies with the logging period - more frequent logs means that the GPS module is downloading fresh aiding data, and stays 'hot', so it will more easily acquire a subsequent fix.
In general around 60s for a 'cold' start (logging period above 2hrs) and 8-12s for a 'hot' start (logging periods below 1hr)
You can also enter your real world device data from the Device Counters saved in OEM (average this across a few devices) to get a more accurate estimate.
To get to the Device Counters, follow the Details link in OEM
The counters are at the bottom of the page
N.B. There are many factors that determine how long batteries will last, do not take this calculator as a guarantee, it is only meant as a guide.