What experience does the surgeon have with patients this age?
Does the manufacturer recommend this interval? (8 years)
What's the actual failure rate
of these pacers at 9,10,11,12 years...?
I think the two biggest risks are the sedation and lead placement if those have to be replaced (more than likely, yes).
I'm a bit leery of giving any advise without more info, but based on what I know and on the outside looking in, I'd say replace it based on options.