Typically the maintenance kits are much cheaper than the printer cost, although this may not be true with small home office laser printers, but cost can vary with different manufacturers. HP is very good compared to others with cost of printer parts and kits. It is recommended by the manufacturer to change these items when the maintenance interval comes around. The parts may last a lot longer than the interval though and you will not ruin your printer if you don't change them. This can vary for many different reasons such as the invironment your printer is in. A warehouse in high heat and low humidity with lots of dust in the air will quickly wear down parts. Using bad quality paper can destroy these parts. Using cartridges that drill and fill recyclers make when they use the wrong toner and the melting point of the toner and the flow characteristics is not correct and builds up on the fuser unit. Not trying to scare you about remanufacturered cartridges but some people out there don't do it right. I'm an expert in the electrophotographic process in laser cartridges so I know what is happening in that industry. The worst that will happen when delaying the maintenance is your print quality will slowly degrade and get worse over time. Normally transfer rollers last forever, only problem is when it gets soiled with toner or when people decide they to screw around with them and touch them with their oily, dirty fingers. The fuser unit does wear over time due to friction of moving parts, paper, and toner. It is possible with some fuser defects to clean the upper and lower fuser rollers from toner, but this can be difficult depending on the fuser and a persons machanical ability. If it gets to the point when you can't tolerate the quality then you can change the parts. The only thing I strongly recommend you do is clean the machine at least because cleaning is normally done during maintenance time and it critical that it is done. Another problem you may see is paper pickup problems due the the pickup rollers or separation pads wearing out. If not too worn you can clean the rollers with a rubber roller cleaner (not alcohol), because sometimes the rollers slip due to build up of paper dust.