What needs to run concurrently is the sponsorship AND the agreement with the strips manufacturer.
Part of the Fans Charter that was drawn up was there would be a minimum of 2 years between changes.
This hasn't been possible due because of the sponsorship recently being for 1 year deals. Some fans may be sceptical and say it's the way the Club negotiate the deal, deliberately only offering 1 year deals, so that fans put their hands in their pocket every year. Others would say there isn't anyone clever enough to think that way at the club.
The 1 year deals also means that the club can get away with changing the template every year.
The thing that has to be pointed out though is we aren't the only club changing strips every year, you just need to look at the new strip thread in Other Football to see that.