How do you know you'll even have an opportunity to turn to God just before you die? A sudden accident or heart attack could claim you -- and then it would be too late. Or you might find your heart so hardened by sin that you wouldn't even want to turn to God.
But the real issue is this: God's forgiveness comes to us only when we truly repent of our sins and honestly commit our lives to Jesus Christ as our Lord and Savior. From what you say, however, you have no interest in repenting of your sins and turning from them -- either now or later. The Gospel of Mark summarizes Jesus' first sermon in these words: "The time has come.... Repent and believe the good news!" (Mark 1:15).
Your question suggests that you also have misunderstood the real meaning of the Christian life. Right now, you think you're having a good time -- but are you really? Some day (as your mother knows), you will reap the consequences of your sins, because sin always has consequences. But most of all, you're missing out on the greatest adventure any person can ever have -- the adventure of walking with God and doing His will every day. Jesus' promise is for you: "I have come that they may have life, and have it to the full" (John 10:10).
Don't be deceived, but turn to Jesus Christ and open your life to Him. God loves you, and life's greatest joy comes from following Him.