Definitely agree with the others. Yes it costs you a bit of extra money and time, and sure its only going to be useful probably 10% of the time, but that 10% could be dangerous moments where you only hear something important because you have the second Radio or are using the monitor function!! Not to mention redundancy of a fairly important piece of equipment.
You'll get yourself into good habits with using more than one radio after your first mistake selecting the wrong comm!! Personally i'm in the habit now where I almost always take a quick glance and do a touch check on the Comm Selector on first changing to a new frequency, only took a couple of transmissions on the wrong frequency and decided to start doing it!