Sea to Summit Waterproof Map Case

I have had just the worst luck with regular map cases. The issue is that the 'zip lock' style of case invariably gets sand in the zip mechanism and then is no longer even water resistant.  Since I am ustually paddling long distances, the cost of waterproof maps is just way to prohibitive, so I am usually found with self printed maps or used non-waterproof charts.

Midway through this trip I was finally able to add the new Sea to Summit Waterproof map case to my kit.  This case is supposedly waterproof by using a roll top closure and then a velcro securing mechanism.  Theoretically, these seem like they would do the trick, so how do they really perform?

The first thing to note is that the case does seem to be fairly immune to the sand issue.  It is easily cleaned and even if you get a little sand, the case stays relatively moisture free.  This should give you a hint about my 'water proof' thoughts.  All in all the case stays relatively dry. The main issue is that water will begin to slowly works its way through the roll-top until getting into the main case.  Heat then makes the moisture expand in the plastic case and you begin to get into issues.

I believe that for short usage, these issues are easily resolved by wiping down the entrance of the case each night and getting rid of that seepage.  For long term use, this just becomes one more task to do each day and is likely not to get accomplished.  The end result is that you then have damp to wet maps.  With waterproof maps, once again, this is no issue.  However, if you are printing your own, the accumulation of moisture eventually becomes significant.  Once that paper gets wet, it is really hard to ever get it dry and then you have perpetual problem.

To date, this is certainly the driest case I have had, however, it still leaves me longing for a truly dry case.  I wish I could get Watershed to make a map case with their patented closure.  My maps would stay dry forever and I would be a happy kayaker.