Years ago on my old house that had just one gutter along the back of the house. They were USELESS. I will say....Might be a Florida thing. It STAYS humid here and mold algae can be quite the PITA. The gutter guards eventually filled with mold/ algae which ultimately grew into the wood behind them, causing a lot of rot. Pulled those damn gutters down, replaced the wood and never had that issue again. Fast forward to 2002....The ex and I had a house built. It came with a small gutter over the front porch. I THOUGHT because it got a lot of sun and no leaves around, it'd be fine. Just out of curiosity, about 3-4 years later, I checked closely and the bolts that held the gutters had rot around them. DOWN those gutters went! Been gutterless since! LOL
I see those commercial / infomercials on the gutter guards and laugh. There is no such thing as a gutter that does NOT need cleaning / TLC with bleach and water. With or without guards.