When trying to find the perfect synonym for "all one can use," there are a few different options to consider. Some possible choices might include: unlimited, infinite, boundless, ample, plentiful, copious, profuse, overflowing, inexhaustible, or bountiful. Each of these words conveys a sense of abundance and plenty, suggesting that there is more than enough to go around. They can be used in a variety of contexts, from describing a limitless supply of resources to highlighting the generous amount of time, attention, or care that someone has given to a particular task or person. Ultimately, the right synonym will depend on the specific context and tone of your writing, but these are all excellent options to consider.