Do power bricks break in?

When I bought my Fosi V3 monos, I thought I’d purchased the 32 volt/5 amp power bricks for each monoblock.  Thinking I wanted to increase the power, I purchased a 48 volt/5 amp GaN brick, which cost about $30 bucks more than the regular 48 volt/5 amp bricks.

They arrived yesterday and when I placed them into the system, I was shocked to find that I needed the exact same volume on the preamp to get the same volume as before.  I then looked at my old bricks and they were actually the 48 volt/5 amp versions.  

I read a review where the person clearly felt the GaN version of the bricks were better than the regular versions.  So I thought I’d do a comparison.  

When I did it myself, I couldn’t really hear any difference.  I then volunteered my son to swap the bricks without telling me.  I only did two tests, but I ended up picking the older bricks the two tests I had him help me with.

This got me into thinking:  Do power bricks require break in?  

What has your experience been with regard to power bricks, if any?

Thanks.