Originally posted by Adam The only limit is your battery life (you can optionally enable a bulb timer which eliminates the need for pressing to close the shutter; this is up to 20 minutes)
I believe the camera comes with DCU. And yes, you can use a 3.5mm to 2.5mm stereo adapter to get many cable releases to work with the camera. There are other threads on this so I'd recommend that you check them for specific adapters and/or remotes.
One last note: you can also shoot remotely using wi-fi, as long as you are happy with the single-frame drive mode.
ad 1) The limit is 20 minutes. If you need more time, you can use a multiexposure mode (1999 shots, each for 20 minutes). So, the limit is the battery.
ad 3) I do not prefer the wireless solution, wifi needs a lot of energy.
NOTE: To be precise, you can also shoot remotely using wifi, and you do not have to be fine only with the single-frame drive mode. There are all drive modes available.