I've been most years since 2005, Kilgoreck, and have never gone more than 18 months between visits and I have been known to go back within 6 months! I'm a huge Cuban dance and music fan and 18 months really is the longest I can go without a fix
I used to go in July for Carnevale in Santiago because I too was tied to education holidays but I don't have the stamina for that now what with the humidity and the fact that the top bands rarely appear before midnight and the festivities go on on until well into the early hours. Getting up for 3 hrs of dance classes starting at 9.30am was getting harder and harder but I was still tempted for this July because it will be commemorating the 500th Anniversary of the founding of the city. I was last there in September 2014 and had been thinking of going back in March just gone but my Dad was hospitalised over New Year and March was too early to contemplate such a big trip and the future was still uncertain at the point when I really needed to book flights for next month too. But I am looking to going back in March 2016 for the Trova music festival and next year might be a double trip because in even numbered years there is a big Son music festival in the October as well.
I can't ever offer any advice re queries about the big AI resort hotels because most of the time I stay in Casa Particulares with local families, even when I do a few days in Havana at the end of a trip. However, staying with local families is a great way to get to know the local culture and and pick up on the features of daily life. Plus the dancers from the professional company I take classes with really have their fingers on the pulse of what's hot and what's not and they really do make sure that we are on the ball and not scammed!
I've seen huge changes over the last 10 years and the pace of change has really speeded up of late - I reckon anybody wanting to experience Revolutionary Cuba has 2 years to do it before it really does irrevocably change and becomes history not lived experience.
SM