The evidence as we have it now suggests that by about the middle of the 7th century (~680-650 BCE), virtually all contact between the Levantine "homeland" and the western settlements had ceased. We have a nice continuous progression of the famous Phoenician red slip pottery, and we find it consistently in the West from about 750 til about 670 BCE, when it suddenly disappears--at least from the sites we currently know about and have excavated. Concurrent with that, many of the smaller Phoenician sites, many of which were totally unknown until the 1960s, seem to be abandoned at around this time. Not always, but often. This includes virtually all of the Andalusian sites in SE Spain (Toscanos, Morro de Mezquitilla, Chorreras, etc).

It does seem that Carthage became the hub of Phoenician activity in the West after this date, and relatively recent excavation by the Germans at Carthage has demonstrated that she was quite large even in the 8th century BCE. Some other important "hubs" were probably Gadir (Cadiz), one or more of the sites on Sardinia, perhaps Motya (western Sicily), and perhaps a secondary site along the coast west from Carthage, like Utica. Mogador remained an important site on the western Atlantic coast of Africa for some time, though a lot more excavation is needed there to say anything substantial about that site.

A good case study for this transitional period is the site Pithekoussai, on the modern island of Ischia off the Bay of Naples. It was the earliest Greek experiment in the west, beginning on or around 750 BCE. The evidence we have there is complicated to explain and to interpret, but the pottery suggests that Pithekoussai was some kind of joint Greek~Phoenician outpost. We find plenty of Greek pottery there, and its imitations, and also that distinctive Phoenician red slip. The presence of pots does not necessarily mean the presence of people, of course, but what signs we have point to cohabitation and/or collaboration. Personally, I believe Pithekoussai was a staging area and rest stop for trading trips going to Etruscan country further north, but that's for another thread. By 700, Pithekoussai is in decline, and by 680 it is totally abandoned. It is possible a natural disaster caused this (Ischia is a volcano), but I think there is more to it. The dates, as we have them now (and chronology can change), fit well with an overall narrative of Phoenician abandonment of the West, at least by those pulling strings back in Tyre and Sidon. The people who were living at Pithekoussai moved to the mainland and founded Cumae, just across the water. But: Cumae looks very different than Pithekoussai. The distinctive elements which usually suggest Phoenician presence are wholly absent from Cumae: no red slip, no lyre-player seals, etc. It seems pretty clear that Cumae is a Greek settlement, and that whatever was happening at Pithekoussai did not get translated to the mainland. Even the burial patterns are different (and burial customs are VERY slow to change, for the most part). And just to throw a wrench in things: there is very strong archaeological evidence that Pithekoussai, already in 750 was tied more closely to Carthage than to the Levantine "homeland."

There would be no further evidence of Phoenician-Greek collaboration after 680, and from then on we have very distinctive Phoenician and Greek spheres of influence and settlement (Greeks in southern Italia and eastern Sicily, and eventually all along the Gulf of Lyon; Phoenicians in North Africa, Sardinia, southern Spain, and western Sicily).

For the Phoenicians in general, see Glenn Markoe's "The Phoenicians" (2000).

For Carthage (but not including some of the important recent excavation by the Germans), see Lancel's (translated) "Carthage" (1995).

For Pithekoussai, see still David Ridgway's "The First Western Greeks" (1992), which is a great summary of Buchner's excavations (and in English not German).

For the connection between Pithekoussai and Carthage, see Docter and Niemeyer, "Pithekoussai: the Carthaginian connection," in Apoikia 1994.