It is definitely easy to just upload a miner virus and wait for that sweet collection time however, you can actually reduce collection time and optimize your maximum benefits. The first thing is that the calculation on mining payouts is dependent upon the amount of CPU that a target has. Secondly, the maximum benefit is determined by the other mining viruses on the target. Let's see how this works below:
If there are no other mining viruses on the target, then you can earn 100% of the targets mining power.
If there are 2 mining viruses then you and the other player will split the resources 50/50 and you will only gain 50% of the targets mining power.
If there are more than 2 mining viruses then the calculation gets a little different.
If you have the mining virus with the highest level on the target, then you actually can earn 50% benefit from the target, while the remaining 2 mining viruses split the other 50% between themselves regardless of their level. So, making sure you have the highest level mining virus on a target (or the only one) will ensure that you receive more benefits than other players and will help maximize your income.
~Slavehack 2 Blog