Bellows Batteries and other things that age

[Chaos]

I'm in the process of up-sizing my boating situation and have a 2005 with dual Mercs in my sights. I've searched the forum for expected bellows life expectancy, but haven't found any info. My concern is that my current '02 had a bellows failure in '08 and I'm wondering if 5 to 6 years is the typical life expectancy or if my previous experience was due to premature failure. For such an inexpensive individual component, it can sure put a hole in your wallet if you're not paying attention.

Well I'm at it, I thought I'd ask about batteries. I'm thinking if the batteries are original, I should ask for new ones.

Any other basic maintenance items like this that I'm missing?

Thanks Mike.