no they don't, aside from canons being carpel tunnel ville, the pirates easily destroy them, and you have to manually rebuild those.
However the uber canon, a 600,000 defender that flys around, insta kills anything, has 50k health, a sheidl, and is never shot at, DOES protect your colonies well (Although they might still loose a building or two, and will not rebuilt it).
You are the only one capable of getting those type of canons by the way, and they require you to grind to unlook the technology.
Yea there are tricks to spice, you can colonize a system with multiple colors, so you get good prices in system, and you can make a system with same color so you visit and max out your hold with 99 spice (you cant have 120 spice of the same type, max 99 of any item, including spice... unless the patch changed that). But it is still a huge pain, and it just seems incredibly STUPID that over 99% of the spice just goes to waste.