The power could vary a bit from 5W but you can probably contact sanwu and get them to send you a unit that is guaranteed to reach 5W.
The laser diode in there is most likely a NUBM07E. Its a Gball diode meaning it has its own focusing lens built into the laser diode. However the lens isn't truly focused to infinity.
The most common solution to get around that is to decan the diode. Meaning removing the protective can and built in focusing lens. This procedure allows the diode to be focused with other lenses. However, the lasing semiconductor die is now exposed to air, instead of being in an inert gas environment under the protective can. This means anything in the air can now react with the lasing die and potentially cause it to fail. Such as: oxidation, reaction to water vapour in air, dust particles fusing to the die (its probably super hot at the emitting point) etc.
I am not sure how sanwu deals with that problem. If the diode used is decanned, then you can expect the laser to not last that long. You can search this forum and see how many times this has happened to our members. If they keep the diode untampered, and use other focusing optics to focus the beam, then you can expect the laser pointer to survive a long time. Based on the pictures, the internal copper heatsink on the silver series looks rather huge, and I will bet that it can do 2-3 minutes of run time with no problem. But I would definitely be nervous to leave it on indefinitely.
If you are using it for academic purposes, and especially if you don't need a handheld setup, I strongly recommend making your own lab style laser with the NUBM07 instead. There are some posts here showing how to rectify the not-so-good infinity focus problem by using a couple pieces of optics. There are some cheap lab style laser kits on ebay that you could use to make your own lab style laser. Get the ones that come with a fan and also make sure the driver has a 12V fan output. Going down the DIY route can be a hassle but it is likely cheaper than buying a pre-made pointer.
Edit: Recently there have been some modified NUBM07E diodes on Ebay. These diodes are recanned with the standard window-style laser diode protective cans (meaning you can now use any lens to focus the laser). They are also filled with inert gas to protect the lasing die. You can also consider using these unmodified diodes in a DIY build.
