How long does it take to level 10-20 chars on Lordaeron?

On Icecrown and Frostmourne I think it takes 15-30 hours to level 5 characters to 80 (I have leveled 5 characters to 80 in 30 hours but if I used hierlooms, didn't loot thrash items and didn't run around taking flight paths and no time spent on professions while also having gold from previous characters, then 15 hours seems doable).

On Lordaeron it is 7 times slower xp. Doing dungeons get really boring when you have to do the same dungeon 15 times with each team and on faster xp servers I think you might save time by doing dungeons since no travel time but that is not really a benefit when it takes so much longer to level.

Doing quests is kinda a must to level on Lordaeron and can't skip many quests because of xp rate, so need to do a bunch of quests that requires looting items on 1 character, wait 5 min for respawn, loot on 2nd character, wait 5 min to respawn...

Some time ago it was possible to loot quest items that drop from mobs with all characters, this was removed so any new team is a real pain to level.

There is also a small speed gain when leveling all the characters at once but split into groups of 5, since then they can help each others kill and more importantly you need to travel less since you can move all characters at the same time. But also means you need to quest in each area so much longer in that play session.

Before I think it took about same time to level as someone that play 1 character, maybe 20-50% longer or something like that. Now it probably takes 3 times as long compared to leveling 1 character but not sure.
I have 10 lvl 80 characters and 5 lvl 70 characters on lordaeron, but I am not on the computer with wow so can't check how long it took for me.

Not sure how long it actually take, but on fast xp it can be fun the entire time since you level so fast and skip the boring parts but on Lordaeron it gets really boring to level after a little while even if it is just 5 characters so a pain to do big teams.