We don't know if it's too high. Bond funds will continue performing well from today going forward, in any of these scenarios:Anyone buying bond ETFs at the current time is likely buying high. I say likely because who knows how low the yield curve can actually go... to zero?
(a) interest rates stay low and don't do much from here
(b) interest rates very gradually creep higher
(c) interest rates stay low and the yield curve steepens
(d) interest rates fall further, to zero or negative
Everyone focuses on case (d) but that is not the only situation in which bond funds do well. Even if interest rates gradually move higher, bond funds will do well. And people don't seem to understand that the yield curve steepening (c) would be tremendously good for bond funds. They start rolling every maturing bonds into progressively better yields.
For all we know, this could be an excellent entry point into VAB. This could even be the best entry point for the rest of your life... we have no idea.