Hybrid Bicycles - Century?

Is it reasonable to try a century on a Trek FX 3/5/6, Trek Valencia, or a Specialized Sirrus Sport/Elite? Or am I best off on a traditional road bike?

This is one of my goals in the next year and I am bike shopping.

You can certainly do a century on a hybrid. You will be faster on a road bike, but if that is not an issue then go for comfort. Ride both kinds of bikes. Buy the one that is most comfortable for you.

Based on what others have said, your most likely problem is lack of hand positions. If you can't change your hand positions, your hands may start getting fatigued more than necessary, making you suffer more than necessary.

Bar ends can help with that, as can swapping out your normal bars for trekking bars.

I'm thinking of riding a century on a "hybrid" later this summer or fall, so I've been thinking of/looking for options.

Sure you can. I've done centuries on my Jamis Coda. You can ride as far as you'd like on any bike you are comfortable on.

When I did the Ms150 I did see some post Y2K Sirrus. Long distances are doable.

I recently did a Trekking bar conversion to my 7.2 with the purpose of doing a double metric century in June. It is a current thread in the forum if you haven't already seen it