Talk:Thief/@comment-64.237.75.135-20140818203949/@comment-8.33.16.141-20161208220013

There's really never any reason to dual class FROM thief unless using a Swashbuckler or Assassin, and in those cases, there are specific levels that are acceptable breakpoints to have minimal waste. Even in BG1 an Elf multiclass is better than a dual along the lines of what Imoen does (low thief/high mage), as you'll never reach the high levels of mage that you can in the sequel and dualling too late will rob you of your thief class while it's relevant in BG1.

13 for a vanilla thief is completely arbitrary, as they still have another backstab factor to gain and it's too early for UAI, you can max Open Locks and  Find/Disarm Traps easily by an earlier level etc.. Adding to this, 14 in mage takes considerably longer to dual back over than an earlier level (mages level quickly until they reach level 11; level 14 mage is somewhere around the Underdark in BG2 with a full party, depending on your side questing diligence!), whereas you can max the important utility skills in thief long before then.

If you wish to get Find Traps, Pick Locks, and Set Traps OR Detect Illusion to 100 each, you could achieve this by lvl 10 with an 18 DEX human vanilla thief/swashy in TotSC, then in BG2 dual over to mage and level quickly to 11, and be done with thief forever, leaving the backstabs to better thieves, a stalker, or ignoring them altogether (backstabs aren't THAT useful considering the vast array of enemies in the game unless you are soloing). If you don't care about Set Traps or putting some into Pick Pockets, you could dual after Find Traps and Open Locks are done at lvl 6 instead and be done with it, also get your thief skills back before the end of BG1 if you have TotSC installed.

Remember that a Mage/Thief never needs Hide or Move Silently. Detect Illusion is an alternative to Set Traps you could take to counter invisibility in BG1 before dualling, but you never really need it if you have access to the proper spells after becoming a mage.

In BG2 (or BG1 EE/Tutu, I guess) Kits are always better fodder for dual classing, so their breakpoints should be considered. Swashbucklers get bonuses at multiples of 5, while the Assassin maxes its backstab at 21. Even Bounty Hunters get their better traps at 16 or 21.