You can experience that the average time span is from two to five years. The basic time of the systems greatly depends upon when the computer is being purchased, the basic changes in a computer is being done in the Hardware and that to the most frequently used software in the computer.
Gradually as the time is being passed it is being experienced that the speed of the system gets slower down with the time. As soon as the time is passed the space in the systems also gets lesser so the need arises to expand the memory size to add the extra files to the computer. The changes made into the computer help to meet the latest requirements of the computer in its software and Hardware.
As soon as these kinds of condition arise the need arises for either upgrading the computer or complete replacement of the computers.
The condition becomes really difficult to judge whether to change the system completely or just to change the parts of the computer to upgrade it in such a manner such that which helps them to use the upcoming latest software as well.
The use of up gradation in computers comes when there is use of a particular application which requires the person more effort. As for that before some time good quality of graphics cards were not available and as for now and the use of the gamers who are engaged in playing games which require high resolution of graphics so they require the good graphic card.
Now days the games that are being developed are of very high resolution and for these type of games a very high pixel of graphic cards are required. Today the quality listening music has gone far beyond the earlier times.