Well, for one they don't show up in this list as often as some others, and when they do it gets patched... unlike some other routers.
Router Bugs Flaws Hacks and Vulnerabilities
Its made by a company oriented towards providing firmware updates as a feature, so as long as the company is viable you should get a longer lifespan out of this as a secure router. They acknowledge that its an industry which produces hardware it never intends to support in the future, and that leaves customers vulnerable. Check out more:
Router Security - Recommended Peplink Router
I dunno if this was the model you thought of getting, but its in that list.
Netgear NightHawk R7000 routers now collect user data | CSO Online