How are they wearing out? Are you experiencing electronic issues or are the ear pads and head band showing signs of wear? The pads and band are easily replaceable and by doing so - one could continue to enjoy these fine headphones for years to come. Beyer is even showing replacement drivers on their web site. After-market pads can have an effect on a headphone's sound profile so proceed accordingly. The Amirons, as I remember from an hour long listening session, may have the highs of the T90s but the increased mids and lows offset those highs. While auditioning, they were definitely a contender.
That being said - As a T90 owner for nearly 10 years, I've found a pair of HiFiMan Sundaras to be a good alternative. The highs seem to be there, but like the Amiron, mids and bass help balance the overall sound. Through my system, my take away is that the Sundaras are a touch more revealing than the Amirons, and as always, YMMV...