An interesting point about the Thousand Yahren War conflict - and also if you study the timeline - is that while the history section seem to suggest that the construction of new ships and materials was a very rapid response to a very serious threat, the timeline shows a gap of some 130 yahrens before the first light cruisers entered service, and a further 77 yahrens before the Battlestars entered service. So, what is going on?

This is all part of the stability of the Colonial society, and belies a possible weakness in their lives. Because their civilisation has been around for hundreds of yahrens, and has remained constant for much of this time, change for change's sake is not the order of the day. When the Colonials design a new ship, they'll build it so that it will last time and the elements. The ship will get upgraded when new technology comes along, but if a single design will do the job required, then a single design is all that'll be built until it can be proven otherwise.

The Heavy Carrier was the only large vessel of the Colonial Fleet initially, then the Light Cruisers came along. The amount of variants of this ship shows this point. It was considered a useful design, and thus adapted to fulfil many roles. The Battlestars came next and variants of them were built based on experience, but in the whole the design of the ship was not changed, and neither was the role.

This does apply to fighters as well, although not as much. While capital ships may have been built many hundreds of yahrens ago, they would be updated with new technology when it becomes available. Fighters are much smaller and less upgradable. While you can gut a larger ship, a fighter is not so easy, and thus new classes would be built as and when needed.