Q. A person who can afford only one suit (jacket) and he would like to wear it both on Shabbos as well as when he davens during the weekdays, is this OK, or does it take away from the honor of Shabbos to wear it on a weekday? If OK, should he remove it immediately after davening?

A. Shulchan Aruch (O.H. 262: 3) rules that one should wear better and specially dedicated clothing for the honor of Shabbos. Poskim disagree as to when is the correct time after Shabbo’s end, to remove those special garments. Mishna Berura (ibid. 8) maintains that one should use them until havdala. The Arizal’s opinion is that they should be worn until after melave malka, since the Neshama Yiseira of Shabbos remains for that time (Kaf Hachaim ibid. 28, Yisod Veshoresh Hoavodo – Shemini).
Yalkut Yosher (p. 58) and others (See Piskei Teshuvos ibid.), assert that the common minhag is to wear them until one goes to sleep. Similarly, they permit wearing Shabbos clothing when attending weddings and simchos, although some are stringent (ibid. quoting Medresh Ruth, Avnei Yoshfo 5: 46)).
In regards to wearing Shabbos clothing for daveninig during weekdays when in need, Horav Shlomo Miller’s Shlit’a opinion is that it can be used for davening.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a