How long can

If you are not concerned about the look, you need to think about the potential of decay, as quite often it is very difficult for an X-ray machine to see under your crowns.  Maybe, a routine replacement at whatever cost would be the answer. 

The other side to the argument is that the more you disturb your natural root stump, the more vulnerable it is to infection.

Depending upon your aesthetic demands, with bleaching, a lot less often.  In other words, bleach your natural teeth to the colour you like and then have your crowns made.  Natural teeth get darker and darker as we get older.  The other alternative, for aesthetic reasons, is to have all your teeth veneered or crowned.  This will give you an even colour for much longer. 

The downside is if any one of these teeth breaks, and you have changed your lab or dentist, it is hard to match these crowns without the right material and colour prescription.  With the latest technology, this problem can be easily overcome using colour measurement guns and digital photography.   

Given that other key factors for maximum longevity are in place, an answer from a purely aesthetic point of view would be that tooth whitening (at the outset of treatment) extends longevity aesthetically.  This is because the colour of the original, natural teeth colour can be maintained to match the restorations (which would have been made to colour match the whitened original, natural teeth). 

As the natural teeth darken with age (compared with crown and bridgework which does not) the natural teeth are then be whitened back to the colour of the original restorations whenever required.

Having all your teeth veneered or crowned at the outset obviously ensures an even colour for much longer. 

Two american studies on the longevity of dental bridges  give  average life spans of nine to ten years. Many factors determine the life span of crown and bridge work. These factors include:

1)   How badly broken down the tooth was to start with, root treated teeth are more brittle and make poor bridge abutments.

2)   The quality of the crown or bridge preparation.

3)   The accuracy and quality of the impression techniques used by the dental surgeon

4)   The accuracy and quality of the technical work to fabricate the crown and bridgework.

The longevity of a crown or bridge can be 30 minutes to 30 years. Many variables require consideration before arriving at the survival rate.

Nothing lasts forever and all restorative dentistry will have a lifespan but a reasonable time scale is 10 to 15 years as long as appropriate care and professional advice is maintained

Crown and bridgework if carried out and planned appropriately in a well maintained mouth can last almost indefinitely, however for insurance purposes in claims I usually estimate that crowns and bridges will need replacing between 15 and 20 years after the treatment has been completed. The average NHS crown is estimated to last between 5 and 10 years so you can see that there are several variables at work most importantly the expertise of the dentist and technician allied to good care from the patient.

The very quick answer is 5- 20 years; this is often quoted in various publications. This is not a meaningful figure because there are so many variables which affect the life of the tooth supporting the crown.  In theory a gold crown for example will last forever.  It is the tooth supporting the crown that is at risk. Porcelain is a wonderful material and can be used to create fantastic lifelike crowns but could influence the longevity of the crown. The factors influencing the life of a crown can be summarised as follows:-

1 Good oral hygiene will help to reduce recurrent tooth decay -perhaps the cause of the initial problem 2 The amount of tooth substance supporting the crown and the nature of the biting pressure on the crown 3 The quality of the laboratory and materials used to create the crown 4 The clinical expertise of the dentist who decided on the design and preparation of the crown.... 

A critical aspect to a crown's longevity is the accuracy of the fit to the tooth. The better the fit the longer the crown will last.  It should be harmonious within it's bite (see Occlusion).