the largest album i've sold was 82 sides, and it's a 2 volume set.
zookbook will bind up to 90 sides - the book will be VERY, VERY thick - and i suggest splitting books this big into 2 volumes because they get so heavy that you can hardly lift them. (i just received one for a client that's about 60 pages and it's easily 5" thick.)
if you are a few pages over the max recommendations, the companies will usually accomodate you, however, the weight is the issue, and the spines just can take the load - so you need to let your client be aware of that.
if our client wants all the pages - since most of my pre-designs lately have been around 70 pages - we will split and bind multiple volumes at no extra charge, although my contract says it's $250. the contract clearly states that the size of the album will be determined by the album company, so that they know the largest single volume size will vary.
hope that helps.