CV Boot Torn. Not clicking No symptoms yet. Drive on a 400 mile round trip highway trip?

I just found out I have a torn CV boot. I looked and its greasy under there and gritty and there is a large tear. I cant afford to fix it for a few weeks to maybe a month. I also have to drive it on a long road trip about 200 miles each way all highway. It has no symptoms yet. No clicking, popping or jerking. I think there is still grease leaking out. The repair place wants to replace the whole axel anyway so I dont think it will cost more. How nuts is it to drive this thing on the trip and fix it later (in a few weeks to a month). Its an 01 Nissan Sentra with well over 200000 miles. Also the car seems solid. Are these cars likely to make it to 300 or 400K without major repair? Are they known for this.