When it comes to design registration protection relating to the UK, and also other parts of Europe (such as the EU), the maximum term of design registration protection is 25 years from the date when the design registration is first applied for. Under most circumstances, this maximum term of protection is perfectly adequate to cover the lifespan of a given design/product.
There are times though, such as for particularly successful products, when this 25 year term is not enough. In these instances, it is not validly possible to preserve the original design registration protection by simply re-applying for the same registered design application again, since one of the cornerstones of valid design registration protection is that the design in question must not have been publicly disclosed prior to the date when the registration is applied for. So reapplying for the same design registration again will mean that the new design registration is invalidated by the earlier/original design registration.
That being said, to the extent any ornamental changes can be made to the underlying product whose appearance was originally protected via the initial design registration, it may nonetheless be possible to protect these changes with a fresh design registration, to help maintain some protection for the product as a whole.
As to what such ornamental changes might be, this could include a slight modification/improvement to the shape of the product, to thus allow a new design registration to be tailored around this particular change in the shape.
Another option might be to modify the surface detailing/ornamentation of the product (such as by using a new colour scheme, or surface pattern), noting then that a new design registration might then be sought for the appearance of the modified surface detailing, to help extend the design registration protection for the underlying product as a whole.
So to the extent any visual change(s) can be made to the underlying product, whether this be a change to the shape, and/or surface detailing, of the product, this change might then form the basis of a fresh registered design application to keep the underlying product protected in some form.
Design registration protection aside, another potent tool which can be used to protect a product whose appearance is particularly striking, is trade mark protection. Specifically, and to the extent one can show that an average consumer of a product associates a visual feature of the product to its underlying owner/brand (such that the visual feature effectively acts as a badge of origin for the product), this can be an indicator that trade mark protection may be a possibility in respect of the visual feature from the product.
As to what such a visual feature might be, this could include, for example, any distinctive colour scheme used for the product, or perhaps the shape of the product itself in some form. Whatever the feature however, and to the extent trade mark protection can then be obtained in respect of it, the trade mark protection then has the potential for an unlimited duration, compared with the 25 year cap for a UK (or EU) design registration. Consequently, trade mark protection can be a fantastic way to reinforce protection directed to visual features of a product - particularly in instances when any corresponding design registration protection for the product may have expired, or otherwise may be expiring soon.
So for those facing the prospect of an expiring design registration, there may nonetheless be some options to help maintain visual protection for the underlying product in some form via one or more top-up design registrations, or trade mark filings. All may not be lost!