50-100 Hours will do the trick...you'll give up a little slam but more than make up with transparency, better tonal coloring and texture...
Note: EH 2A3 and other popular Russian 2A3 plus the current bigger sized Shuguang 2A3 are all 300B/2.5V by design. Cary amplifier and many other current 2A3 amplifier makers are deisgning the amplifier at much higher plate voltage than a typical RCA standard 2A3 is calling for.
The majority of today's 2A3(actually 300b/2.5V)have already changed the landscape of 2A3 for good. RCA 2A3 is of smaller power thus becoming less less due to the supply of real RCA format 2A3. Sophia Electric is making a real RCA formate 2A3 mesh plate, however, the demand for it, is less than its more power 300b/2.5 cousin for most 2A3 users. The lack of affordable good sounding speakers and speaker drivers are the reasons.