People seem to believe it to be true! they say.... it depends on how many items you have in your pack/bank box and maybe pets in stables as well. the less you have, the less laggy you're likely to be?
I dunno, I never really tested it.
I have never tested the lag part, but I have seen evidence that once opened your bankbox stays with you. I had seen it in the past and tested it again this morning.
I logged in and went to dungeon abyss on the crystal portal (aka Tomb of the Kings or I call it the Ord/An-ord dungeon). I went down to the large room with the undead gaudians just before the cave. I hit ctrl-shift and saw no items. After killing a few creatures, ctrl-shift would show some items from nearby bodies. I recalled to glow bank and opened my bank box, then home and used the portal again. When I got back to that room ctrl-shift showed a scroll of valient commodation, two practice longswords, moonstones, bandages and a bracelet - all items from my bankbox.
I did this in EC with Pinco's active. When I tried in CC with UOA, the items did not appear.
A question I just thought of while doing this is - when you use the item insurance menu the entire bank balance (gold and checks) is shown. is items info also sent?