Harpo,
Yes you can buy two Everstarts for the price of one Trojan( a little more $ but whatever) but what you wont get is the reliability or performance. I doubt you will get more life out of two everstarts, at least thats been my experience.
I have never gotten more then a season out of an Everstart( normally less) ever and i have run a few. Same with Interstate, duralast, etc ( all the same battery and yes i have run them with no success). Every time I have had one of tese batteries fail it has either screwed up a tournament, or worse totally botched a weekend of fishing in some far away place. When you maintain something like its your job only to have it fail at the worst possible time is really a drag, thats my experience with the Everstart. Honestly i think its the rough water i boat in but a marine battery should be able to take the abuse. My Trojan batteries have taken the abuse and for 4 seasons.
I have heard the argument that you can just go to walmart and swap them, well thats true as long as 1) There is a walmart nearby 2) You have the recipt with you and 1) They have the batteries in stock( that has been a problem for me in the past). Then when you figure the pro-rate charges in after a year the walmart batteries become quite expensive when they fail like they have for me.
I have 4 seasons on my scs 225 Trojans and they are showing no signs of giving up yet. Thats 4 seasons of fishing just about every weekend( both days) from April to November with over 20 tournaments mixed in per season. The amount of money i would have had to spend on Everstarts in the same timeframe would have cost me over double what the one set of Trojans did. And with the Trojans I have had no reliability issues, no failures on the water, no ruined weekends and i dont run out of juice because they flat out perform better. Personally i would rather spend a little more upfront and not have issues and get the performance i want. Sure you can have issues with a Trojan battery but your are less likley to, they have a much better track record.