Meaning of LONG in English
BAD : I'll go with you as long as I won't have to sing.
GOOD : I'll go with you as long as I don't have to sing.
BAD : I am afraid it will take long to improve my English.
GOOD : I am afraid it will take a long time to improve my English.
Use take long in questions and negative sentences: 'How long does it take to get to London by train?' 'It doesn't take very long.'
Use take a long time in affirmative sentences: 'It might take a long time to sort out the problem.'
Longman Common Errors English vocabulary. Английский словарь распространенных ошибок Longman. 2012