Route Planning, when it comes to the ride...

sorry that was a rant. my reasoning and justification of buying a Garmin.
If it helps I've been deliberating over purchasing a Garmin for a month or so now. I can see many upsides and a few negative. As the benefits are relatively obvious I've listed the negatives and am currently weighing those up from a logical aspect.

Battery Life - 15hours. I plan on lots of rides which could take upwards of that time. This makes the Garmin a poor choice unless I can find an backup battery pack which runs on AAs (The same as my lights). This becomes essential during things like touring and other multiple day rides.

Cost - It's a lot of money but my current concept is thus, Maps of all of the places that I wish to ride would add up to a similar if not more excessive cost. The Garmin is just outlaying all of the cash at one.

Lack of GPS Signal - Without using one I've no way of knowing how often it will lose signal. For certain rides this could mean taking paper based maps too.

...

I've basically worked out that the best solution to my situation is a mixture of the following, paperbased maps (pages ripped out of a road map) or handwritten route notes for rides that I have already done. This will jog my memory on the bits that I forget or fail to recognise.

Use of a normal cycling computer for average speed, distance travelled, top speed etc

Garmin for longer touring rides, completely new routes and attempts to join different bits of rides together.

The versatility of having all three seems to me to be the most logical solution. It means that I can conserve battery life on the garmin when needs be, not worry about using it on shorter or training rides but still have the requisite numbers from the computer. Carrying a road map of an area of the country that I don't know just makes sense to me, useful in the unforseen circumstances whcih will always crop up somewhere.