You have been incredibly fortunate to have your Toetoe survive for thirty years, as this is far beyond their expected natural lifespan. They are generally very hardy plants, being reasonably resilient to wind, waterlogged soil, salt spray, and moderate drought. 

Ideally, it would be worthwhile purchasing new specimens. There are usually three species available, Cortaderia fulvida, Cortaderia richardii and Cortaderia splendens. 

Always select a young, bushy specimen, avoiding any old, tired-looking plants. Toetoe do best in a sunny site with moist but well-drained, fertile soil. Prepare soil well before planting your new specimens by adding Daltons Garden Time Compost. 

In terms of ongoing maintenance as the Toetoe grow, and to reduce a “dried out base,” cut and comb out the previous year's stems and any dead leaves in late winter or early spring each year to encourage new growth.