I built up a pair Encores with the full premium parts specification (Mills resistors, tube connectors, SoniCaps and Miflex copper by-pass caps) last summer while recovering from my hip replacement, and listened to them for a for a bit, but then had to put my Harbeth 30.2s back into the system as my reference as I had three components come simultaneiously for review at TAS around November last year. After completing those three reviews, I had some "down-time" of about two months between new gear arriving for review*, so I set up the Encores again. Now last fall, when I built up my pair of Encores, I asked here how much run-in/burn in time they needed and received responses that they needed about 25-30 hours to run-in.
Well, an audio buddy came over in May to hear the system and was fairly impressed with the Encores (especially at their price), but as soon as we switched back to my 'Beths, he moved his arms out expansively, gesturing that the Beths were much more open, spacious, full-bodied, and as Hans Beekhuizen says, "relaxed-sounding". He was correct. I figured that the Encores simply had not enough run-in/burn-in time on the clock, so the following week, I called Danny for some insight. He asked me how many hours I had on my pair, and when I told him about 15-20 hours and that gang had said they needed 25-30 hours, he replied (and I'm paraphrasing here);
"No, no way. With the standard premium parts (Sonicaps, Mills resistors, etc.) they will need at least 200 hours. With the Miflex copper caps you have for the "upgraded" premium parts, they will need at least 400 hours to burn-in those caps."With that, I was a man on a mission, and set up my Encores as my home-theatre mains and ran them for 8-10 hours a day on a range of content (spoken word and music in movie soundtracks for example), tracking their hours daily in an Excel spreadsheet. I powered them down overnight to help with forming the caps.
At 275 hours, I set them up along with my way-cool little Nelson Pass Amp Camp amps (to get some burn-in on the amps as well) and running the ACAs as bridged monos, and it was clear the Encores had started to open up, and sound fuller. Undaunted, as I had a trip up to Washington state the week of June 8, I set them up with the home theatre system playing classical music, and let them run for 5 days straight on the AVR.
My math told me I had ~425 hours on them and at that point, it was clear the Encores have fully arrived. They now sound much accurate and lifelike with respect to tone, timbre, rendering of instrument and vocal textures and harmonics, but also are notably improved with respect to producing responsive power and ability to "scale", a trait I've termed "dynamic slam". The mids were notably more open, full, and natural-sounding, the bass response went lower with better definition and articulation, and the imaging and soundstage as a whole was more open and expansive yet providing focus for instrument and voice imaging within the sound field.
Bottom-line: if you buid up a pair of Encores with the the Sonciaps, Mills resistors, and tube connectors, etc., figure on 200 hours of run-in. I would say more like 275 hours, actually. With the Miflex copper caps, you'll need 400-425 hours for them to fully run-in/burn-in. I will add that Danny's input for the burn-in for these parts
was 100% accurate and on-the-money with the burn-in time required.
My recommendation: build 'em, burn 'em in and then, sit back and enjoy!
*– just yesterday, though, the Conrad-Johnson ART 150 stereo amp arrived, and soon, the TOTL $39K Linn DSM DAC/streamer. 
