Thargoids ? No such thing. A bunch of BS told by old grannies
I get interdicted on the average 1 to 2 times in a 400+ Ly trip back to the bubble from Ceos/Sothis. I hardly get scanned, if ever. Most scans occur near the mail slot entrance to stations and those are easily avoided by being efficient with your ingress. I will say an average of 0 to 1 scan on the return leg of the trip. Bear in mind, most missions at Ceos/Sothis is for legal haulage and so concerns about ship scans and cop stops is moot.
That's a pretty low interdiction rate compared to some of the stories I heard with folks doing Robigo Runs.
I think that has to do with the number of missions you stack at Ceos/Sothis compared to Robigo.
Ceos/Sothis generate long haul missions where you carry 8 to 140+ units of cargo per mission. Usually I go for missions with 8 to 40+ tons of cargo and this translates to about 4 to 6 missions in order to fill up my Asp.
AI interdiction, despite their increased aggression in 2.1, is childishly easy to evade. If interdictions are bothering you, you are doing something wrong.