Most of the water damage we see in Houston homes didn't come from a roof leak. It came from a gutter that was full of pine needles when a summer storm dropped three inches of rain in an hour. The water went over the edge, down the siding, behind the fascia, and into the wall.
A gutter that can't drain does three things: it rots the fascia board it's attached to, it dumps water at the foundation instead of away from it, and it pulls loose under the weight of wet debris. All three are far more expensive to fix than a cleaning.
The right time to clean is late spring, before the heavy summer storms, and again in late fall after the leaves come down. If you have pines or live oaks overhead, add a mid-summer check. While you're up there, look for downspouts that are disconnected at the bottom, seams that drip, and any section that sags.
If ladders aren't your thing, this is one of the most common items on our maintenance visits. We clean the gutters, flush the downspouts, re-secure anything loose, and tell you if the fascia behind them needs attention.