[bob1029]

I've got the opposite experience. Most rewrites I was on had substantial uplift in the product value.

The trick is to engage with the customer early, directly and often. If the customer isn't willing to pay more money for something, you should probably not do it.

[t43562]

If the effort is too large then you might take years to get to the end - always trying to match the old product (which evolves) and eventually realising that your new architecture isn't perfect either.

I think it can be extremely good to rewrite small things - you always know how to do it better after you've done it once.