Audio Horizons TP 2.0 Preamplifier

Anyone famaliar with the manufacturer,and in particular
this pre amp.The credentials and testimonials seem
impressive.The advertised 10 day audition is appealing.
The site is still operating, but no mention yet of the new amp lines.

The power amplifiers are SETs. So far, an EL34 (~6 watts per channel) and an 845 (~25 watts per channel).
Has anyone who has had an early 2.0 model had to change out the four E88cc tubes yet? Mine are still original Siemens Cca and I don't have a clue how many hours I have on them. I'm curious what to listen for when the tubes are showing their age and need replaced. I'm trying to get the most out of my tubes because they are rare NOS and expensive.
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