Which DLC are safe to untick once I am done with them?

[Nepro]

I've been always playing with all DLC and I can't make distinction between them. Which DLC are safe to untick once I am done with them? I mean DLC strictly related to the quests/houses/ etc. I don't want to lose items.

[gregathit]

Hard to definitively say as I don't know what armor\weapons you have, nor what you have stored where.

Spell tomes and Orrery should be relatively safe to disable - you may loose a spell or two but I don't ever enable these so I am not sure how much of a loss it is (if any).

Thieves Den, Vile Lair, Wizard's Tower (Frostcrag) and Fighter's Stronghold should all be fairly safe to disable provided that you gather all your loot from them.

Horse Armor, Mehrunes' Razor and Knights of the Nine - if you have completed them and you disable them - you will loose all the weapons\armor you gained from them (meaning the items 'added' by the dlc - vanilla items will be fine).

When in doubt as to what the DLC contain - just look at the wiki: http://www.uesp.net/wiki/Oblivion:Official_Plug-ins