Repeated themes are essential to sung-though musicals, but should be used sparingly and thoughtfully. Lloyd Webber overuses his themes in POTO as filler throughout more than 50% of the score. Most of the time, without any thought or meaning. In Les Mis, the repeated themes were often connected to a specific character or mood to support the book. Listen closely to POTO and you will hear Angel of Music 11 times as an all-purpose scene change filler. Act 2 only contains 3 songs not heard in the first act: Masquerade, Wishing You Were Somehow Here Again, Past the Point of No Return (the latter two being the weakest of the score). He did a much better job with Evita, JCS and Aspects of Love (and even Starlight Express).
I worked the POTO national tour twice and have a huge respect for the design elements of the show, but the score makes me just a teensy bit nauseous. Honestly though, take away the eye-popping sets, costumes, and lighting and you have a very long and dull evening.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian