The way HLA are made they will "inflate" quite easyly but are very hard to "deflate" that's why you have a check valve in it...if they "deflate" easyly then you'l loose lots of cam lift and duration...
on some car when do you a head or cam job you have to reinstall al lthe parts, wait 1 hour and after that you start the engine reason for that is to compress the HLA to their new installed height

 

How can that make any difference? if the cam
isnt turning, only a small portion of the HLAs
will be under any pressure, the rest will be just
sitting there, waiting for the cam lobe to come around again.

The shop manual suggests upto 15minuts of idling
<3000rpm to remove the tick from a HLA.

 

The reason for that is to compress the HLA to their new normal operation height, when a HLA is "pumped up" the valve will still be open when the cam is on its base circle (where you get no valve lift)surely the HLA wich are righ on the nose of a cam lobe will "deflate" too much but they will be quickly "pumped" to the right height with the engine oil pressure while the ones wich sits on the base circle will be at an almost correct operating height
i didn't invent the 1 hour wait time,it's a general rule of thumb to avoid problems
some cars need more time to bleed down the HLA while other bleed down quite fast
Random did confirm that some HLA take time to deflate with his compression test