No repeat visits that we know of. The idea of Thule did stick around, but everything that was claimed about it by other ancient authors was unverified because they only had Pytheas' word to go on, often with Eratosthenes as an intermediate source. And the information they had about its location is very muddled: Eratosthenes seems to have thought it was on the same meridian as Alexandria (30° E), but most sources put it directly north of the Orkneys (3° W); it may be that the Eratosthenes thing is a misunderstanding, and he was just citing Thule as the farthest north land known to him.

Much of what we hear comes from Strabo, who sometimes cites Thule but only as an illustration of Pytheas' unreliability. Here's one of the main bits (Strabo 2.4.1-2, tr. Roller):

Pytheas, by whom many have been deceived ... he asserted that he traveled over the whole of Brettanike [Britain] that was accessible, reporting that the circumference of the island was more than 40,000 [stadia, i.e. 7400 km!], and also recording matters about Thoule and those places where there was no longer any land in existence -- and neither sea nor air -- but something compounded from these ... he adds that when he returned from there he went along the entire coast of Europe from Gadeira [Cádiz, S Spain] to the Tanais [the Don, NE corner of the Black Sea].

Now Polybios says that this is unbelievable ... Eratosthenes was at a loss whether to believe these things, but nevertheless believed him about Brettanike and the regions of Gadeira and Iberia. ... I have said that Eratosthenes was ignorant of the western and northern parts of Europe.

At 1.4.2 Strabo tells us that Thule was supposedly six days' sail north of Britain.

As I mentioned, much of what people knew about Thule was filtered through Eratosthenes' Geographica (also lost). Eratosthenes knew Pytheas' On the Ocean, and plotted Thule on his world map based on Pytheas; some of his information about Celtic placenames probably came from Pytheas too. But we don't know how much or in what way Eratosthenes processed Pytheas' data. (See further Roller, Eratosthenes' Geography, 2010, p. 29.) We do know he treated Thule as being on the same meridian as Syene, Alexandria, Rhodes, and the Hellespont, which is obviously inconsistent with being due north of Britain. But ancient mapmakers had great difficulty with longitude. If you look at these places on a modern map you'll see that Eratosthenes' meridian wriggles east and west quite a lot. It's clear that when it came to the North Sea, there was a lot of fudging of the coordinates -- which probably also explains why Ptolemy thought Scotland was a narrow strip of land running west to east. (As Strabo said, 'Eratosthenes was ignorant of the western and northern parts of Europe.')

The geographer Marinus of Tyre plotted Pytheas on his map at a latitude of 63° N (FGrHist 2114 F 1). That's also where it appears in Ptolemy, Geographia 2.3.32, 2 degrees due north of the Orkneys.

(By the way: if the reports derived from Pytheas are correctly reporting the 6-day sail-time, the 63° N latitude, its size, and its direction from the Orkneys, then all of that together pretty much solidly points to the Faroe Islands as the place Pytheas visited.)