Hi! INTP and 20-years qualified Myers Briggs Consultant here!
It's OK to take MBTI more than once in your life, but maybe not more than once a week! Scores in the questionnaire may vary because of context (work v play?), life situation, etc. This doesn't mean the result is 'wrong', because the questionnaire is actually only the first stage in establishing your 'type'. It produces the correct result immediately in about 70% of cases, but there are two further stages to go through before you get a really reliable outcome. The first of these is what's called a 'best fit exercise', where the Consultant explains the theory and invites participants to self identify (before being given the results of the questionnaire), then finally a client MUST be offered a proper 'one-to-one' with a qualified person to resolve any particular personal questions.
Without all three (potential) stages it may be entertainment, but 'Myers Briggs' it ain't, sorry!
Chris
(Happy to answer questions, here or by pm)