I am not talking about those 1 time use cameras. Those entry level SLR cameras are probably design to last 5 to 10 years for amateur use. The shutter might last 20 to 30,000 cycles or so. After that, it is finished, or to be disposed. Ken Rockwell said that it is better to buy an F80, use or abuse it until it konks off, buy another F80 than to get the F100, which is heavier and cost more than 2xF80. Interesting view.
Now, for those consumers lenses, say, costing less than 500 bucks could be viewed similarly. Lenses do not finish, but collects dust in the inside as we use it, focusing and zooming, exchanging air with dust-filled air. After 3 to 5 years, when there is enough dust to affect the sharpness, the flare and the contrast, it is about time to dispose it. It is also time to get new gear that is faster to focus, lighter to carry around, using smaller filters, cheaper to buy, more convenient to use, with IF, ED, lens motor, AF/MF switch. APO etc, etc.
Tripods and ballheads are different. A good Manfrotto ballhead could readily last 10 years and beyond. Those older aluminum tripods, being more solid could last as long. Newer carbon fibre ones might be less robust. Only check if the screws, pins and rivets are made of stainless steel, then, I am quite sure such gear would last longer than you expect. Most of the time, we get new gear becos there are always better designed stuff out there to tempt us - lighter, more sturdy, more convenient to use, etc.