I suspect the author in that sentence hesitated between often and most of the time: he wanted to indicate that it was helpful very, very often; but he didn't want to go so far as to say that it was helpful more than 50 % of the time, and so he chose a somewhat cowardly expression in between. I think he would have been better off choosing either often or most of the time, or perhaps very often, though I don't think the added intensity of very is really necessary.
Most of the time is an expression indicating that something happens more often than not, usually much more often.
Much of the time I would normally only use where you could not substitute often, a simpler word, which is the case especially when it is about a large chunk or chunks of a period, not merely a frequent number of times.
They arrived early at the aeroport. They had wanted to spend their final hours in romantic embrace, but they were busy looking for the right papers and documents much of the time.
This means that a large part of this time was spent looking for papers, but "large" could be anything from 1 % to 99 %; if I used most of the time, it would mean that more than half of the time was spent on it.
They are equivalent and interchangeable terms in the example given. My suspicion is that the writer simply didn't wish to use the same word twice in one sentence. There are variations of meaning between the two words, but in this context they mean exactly the same thing.
Best Answer
onetime, one-time:
one time: