I’m one of the people who has used the Ecolink open/close sensors to connect to my old home alarm wiring. My old system had 6 zones, but many more sensors…some are daisy-chained together. All of them are hidden/flush magnetic reed switch-type sensors, and all of the wiring (windows, doors, siren) is centrally located in one of my closets. Therefore, I bought 6 Ecolink sensors and wired them to each of the zones in the closet. Works perfect. I haven’t noticed any attenuation/distance problems and some of wiring is pretty long. I did have to cycle each zone once for the Ecolink to report the “state”.
Additional note: I purchased my Ecolink sensors with the GoControl Premium Security kit (3 sensors, 1 motion, 1 siren), since I also wanted a siren and this was the cheapest route. I bought two kits, so I currently have 1 spare siren and 2 spare motion sensors.