I have engaged a lot with the topic of antiviral treatment in the past year, so perhaps I might also contribute some experiences.
I think there is three groups of people
(1) Those who use antivirals to combat particularly nasty or recurring herpes outbreaks, esp. cold sores.
(2) Those who have active herpes virus infections (esp. EBV, CMV), i.e. positive IgM antibodies and/or evidence of viral DNA via PCR over a lonter period of time.
(3) Those who don't have positive IgM antibodies, but may have positive EBV early antibodies and/or high CMV or HHV6 IgG titers and who are using antivirals per Dr Lerners protocol (see
@Hip's post).
For group (1), low doses might just work fine. Group (2) can start on a lower dose and see if it works, i.e. if the IgM goes down, and if it doesn't, can up their dose.
The tricky case is group (3). As
@Hip pointed out, the idea behind Dr Lerner's protocol is that CFS in some patients is caused by ongoing (incomplete) herpes virus replication that cannot be detected by today's blood tests (except some evidence for EBV early antibodies).
Dr Lerner suggests to use high doses of antivirals over a long term to drastically reduce the herpes virus in the body and those reduce or stop virus replication that is causing the symptoms. For EBV, that means high-dose Valacyclovir (Valtrex), and for CMV and HHV6 it means high-dose Valgancyclovir (Valcyte).
I'll explain the rationale for EBV, which is what I have, but I think it's the same for CMV and HHV6.
The idea behind Dr Lerner's treatment is to stop EBV replication to an extent that does no longer infect new B-cells (the virus reservoir) during episodes of reactivation that periodically occur in any infected person. B-cells - both infected or uninfected - are replaced in about 3 months, so if EBV replication is stopped over many months, the number of infected B-cells is expected to fall and the damage EBV can do to the body is reduced.
For this purpose, a rather high dose of antivirals is required, as Dr Lerner says, it is imperative to reach the IC50 concentration (when 50% of viral replication is stopped) over 85% of the day. Dr Lerner's protocol, therefore, is 4000mg Valtrex a day (1000mg every 6 hours) and even 6000mg for those above 80kg weight.
There is evidence that lower doses could also accomplish that goal, but it may take longer. For instance, a 2009 study demonstrates that even 500mg once daily can reduce the number of infected B-cells substantially:
http://jvi.asm.org/content/83/22/11857.full
The same study concludes that long-term Valacylcovir treatment might even be successful to eradicate EBV from the body (over several years), however, for this purpose, a dose of 3000mg a day (1000mg every 8 hours) would be required for several years.
Dr Lerner also mentions that after 12 months of treatment, many patients can reduce their dose and still retain the benefits.
My personal experience is that I had fantastic benefits with the high-dose protocol of Dr Lerner in the first 6 months. Joint pain totally disappeared (could hardly walk from bed to kitchen before), PEM is almost gone, heat intolerance is much better, fatigue and concentration are somewhat improved.
Valacyclovir is a relatively safe drug and is well tolerated by most people even in high doses and over longer periods of time. However, it can affect the kidney and this has to be monitored. I developed some problems with the kidneys after 6 months. As recommended by Dr Lerner I did regular blood tests every 6 weeks and it showed that kidney function deteriorated. I then had to switch to Brivudin which is a different antiviral that doesn't affect the kidney. My feeling is that it also helps to some extent, but that it is not nearly as effective as Valacyclovir.
I am now starting Valacyclovir again at 5000mg a day instead of 6000mg (5x 1000 instead of 4x 1500) and hope I can tolerate it.