For the CT, I'd say yes. They are moments here and there, such as when they separated from Luke while he's fighting Vader. But on the whole, I feel the concept is strong here. For the PT, it doesn't seem to be. For TPM, R2 isn't seen until the escape on the Naboo Ship. And then C-3PO isn't seen until later. We also leave him behind until AOTC. R2 is stuck with Anakin, leaving the adventures of the Jedi and Padme unwatched. AOTC doesn't get away either. R2 is with Padme from the beginning to be sure, but no-one sees Kenobis' adventures. The Droids don't meet him until the Arena. And again, 3PO isn't seen for the most part. They are all reunited in the arena, but are separated again from the main viewing again, not to be seen until the wedding. Lucas may fix this in EPIII by keeping the droids close, but have the first two films damaged the idea of the saga being watched by the droids?