I am not a native speaker, but I am writing a poem, where on a certain line the main character expresses the idea that he wants to reach an age of at least 90 and a couple of years more (not specified how many exactly). I used dictionaries and Internet but cannot find a clear answer. I am thinking of the following line: "It's ninety plus to which I strive". I want to use the word "strive" because of the rhyme. Rythm and metre are also important for me. Some fitting alternatives for "to which" might be: "for which", "whereto", "wherefore". Which of these four is correct (or the best)?