Ahh !!!! more light is shed.
Malechite is very effective, and ich (to the best of my Knowledge) won't build up resistance very well. However, one of the major downsides to meds (IMHO) is how they work. Malechite and many other effective parasite meds work by breaking down protiens. The more organic matter you have in the tank, the more protiens there are to "use up" the meds effectiveness. Organics in the tank are IMO the largest vairiable working against meds, and if you adoprted a mess, you stand to have high organics. Since we don't really know the protien levels in a tank, the dosages reccomended are arbitrary, as is the time between dosage. Additionally at lower temperatures treatment needs to be extended. I reccomend a minimum of a week ( I personally go 14 days) after the last visible spot in a tank at 80+ *F in a tank at 72* F I would think 2 to 3 weeks would be more the safe period. I do not know exact time frames based on temp, but I do know that coldwater ponds with ich can take some really extended treatment periods to finish off ich completely. So despite the effectiveness of Malechite, the odds of your first treament being successful are slim.
Salt is not effected by organic levels, and therefore that vairiable is removed, additionally, salt is far less stressful than extended use of meds, and therefore the treatment can be maintained at full strength for as long as needed plus a week or two for insurance. Remember that the reason meds irritate fish is that they attack protiens. Dosage amounts are designed to be enough to kill ich without being enough to kill your fish. Most fish can and will tolerate salt use quite well. Most of the ill effects of Salt are long term weakening and damage, not short term irritation.
The next thing I would add is do not let ich discourage you. read the article linked above, or research others with good accurate information, and then take the ich out permanenetly. Ich is a pain, but it is also an issue that you can deal with and put behind you. tearing down a tank and sterilizing it is more work than treating for ich 5 times would be (IMHO).
Good luck and keep us posted
Dave