Borderlands – What gameplay effects change in multiplayer

The shops change inventory every 20 minutes. There is a convenient countdown timer under the item of the day.

The only exception is if someone currently has the shop open, the items won't switch until everyone is out of the shop interface.

The length depends on the elemental damage type. I found these out by testing with Target Practice in Marcus' shop in Sanctuary.

• Fire: 5 seconds
• Shock: 2 seconds
• Corrosive: 8 seconds
• Slag: 8 seconds

This means a Corrosive gun with the same damage/second as a shock gun will deal much more damage than the shock gun if you let the effects linger. It also lets you stock a lot more Corrosive/Fire effects on a single target than you can Shock effects, but Shock effects will usually drain a shield so fast you can switch to another weapon to deal the health/armor damage instead.

Note that certain enemies resist these damage over time effects entirely, and bosses may take elemental damage for much briefer periods of time; for instance Terramorphous can only be Slagged rarely, and when it worked Slag only works for 1 second. Most normal enemies don't have shortened effect times however.