There is a din in the gemorah (Chullin 110a/110b and likely elsewhere)
ואמר רב יהודה טלית שאולה כל שלשים יום פטורה מן הציצית
A borrowed tallis does not require tzitzis for 30 days (my paraphrase)
(and therefore many have a custom not to recite a blessing on a borrowed tallis). If, say, I am praying shacharis with a borrowed tallis and tfilin, is there any point in wearing the tallis?