A story is told of a man who wanted to write a will, leaving an extremely large sum of money to Torah institutions after his passing. He asked the Rebbe Rashab how he should proceed. The Rebbe answered that instead of figuring out and worrying how his money should be spent after his long life, he would do better to give charity during his long and healthy years. That way, he would derive pleasure and enjoyment from seeing how the institution benefited from his charity immediately.

Sefer HaSichos 5697, vol. 2, p. 188;
Toras Menachem 5711, vol. 2, p. 189