If it's constant up and down, go with lower gearing. I don't know what everyone else considers to be a hilly century; I give one a 'hilly' rating when there's over 6000' or more of climbing.
A triple isn't necessarily over-kill, but it could be more total gears than you need since you can accomplish a similar gearing range with a compact double and a wide-span cassette. You don't have the tight configuration of 1 tooth jumps for cruising the flats any more, but it's a reasonable sacrifice. I have a 34/48 up front, and an 11-32t cassette. My daily commute is 30 miles r/t, with a bit over 2000' of climbing and I'm signed up for a 7000'+ century next month, so I'll really get to test out how this gear range performs.
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