A sister left this question in the comment box and I thought I would write a long response to it sp I might as well do a whole seperate post since this is something I have contemplated myself before, when I started to wear hijab, and now that I have decided that there is a good chance that niqab is part of the jilbab (for myself---please no one feel that I am pushing that, this site isn't a fatwa site like Islam Q&A okay). Here is her very valid question:
Q. I'm considering wearing niqab 3 months during my summer holidays, as I'm going to spend it inshaAllah with my husband, who is abroad. But does it makes sense if i know that i'll take it off afterwards?
It wholly depends if you believe the niqab is fard/ wajib (an obligation---and part of what Allah subhanhu wa ta'ala requires of your dress) or if you believe it is mustahaab (there is reward if you do it). When I first started wearing hijab I didn't think hijab was a fard requirement. I hadn't read the Qu'ran yet but I saw Muslim women wearing it when they prayed so I tried it on from time to time. When I read the Qu'ran and learnt the hijab was a requirement, I put it on and did not take it off. Same with when I read about jilbab. As soon as I had enough money to buy a jilbab, I always wore that also when I left my home. If you believe niqab is an obligation on you, then it is a sin for you to leave it off. If you simply believe it is a good deed for you to do, that is pleasing to Allah subhanhu wa ta'ala then if you only do it for a day, that day is still pleasing to your Lord. If it is easy for you to wear it abroad, then you should wish to do those things that are pleasing to Allah subhanhu wa ta'ala that you are able to. But, Allah's Messenger (sallalhu alahi wa salaam) said: "The most blessed of deeds is that which is done consistently, even if it is a minute one" [Sahih Bukhari]. So with mustahaab acts doing the act conistantly is more beneficial than doing it rarely, or intermintently. Of course, any good we might do, even if it is only one day, or one week, or three months in our lives, is good for us, should Allah subhanhu wa ta'ala accept out intentions, knowing they are for His glory and mercy and love alone.