Line-number BASIC requires good planning in general. Too bad nobody taught me that little secret as a kid.
Remember to breakup your sections or routines ... If my code is extra long I usually keep data and UDG stuff at the end of the code around line 6000 or 8000. Data statements can usually be placed sequentially so incrementing line numbers by 1 or 2 is usually okay here.
GOSUB 1000
1000 REM --- Describe and add comments
rest of code
2000 RETURN