Notice the verse puts two CONDITIONS of hearing and believing upon having eternal life:
"He that heareth my word, and believeth on him that sent me, hath everlasting life,..."
How can I "notice" something that doesn't exist?
Where do you see the word, "condition" in that verse?
Both verbs hear and believe are present tense showing an action that is currently ongoing and sustained.
You are ignoring the distinction between grammatical "active" tense, and experiential "activity". Yes, we "hear", it is something we do. But it is not something under our control that we can "choose" to hear or not hear something. Whether we can hear or not depends on God, not us.
There is also the added complication that the Greek word, "akouo" can either mean "hear" (physical sounds/words), or "understand".
As for "believing", while it is common for people to ASSUME that believing is something we can "choose" to do or not, the Biblical truth is that if God gives someone faith (Eph. 2:8, Phil. 1:29, Rom. 12:3, 2 Pet. 1:1, 1 Cor. 4:7, etc.), then they WILL believe. And if God doesn't give them faith, then they can't. This is what Jesus taught:
John 10:26 but you do not believe because you are not among my sheep.
Notice that it does NOT say, "you are not my sheep BECAUSE you do not believe".
It says, "You do not believe BECAUSE you are not among my sheep".
If you are not Christ's sheep, you cannot believe.
Luke similarly limits those who are able to believe:
Acts 13:48 And when the Gentiles heard this, they began rejoicing and glorifying the word of the Lord, and as many as were appointed to eternal life believed.
Meaning if one quits hearing and believing he will not have eternal life.
One of the problems here is that your STARTING premise is that we "can lose our salvation". So you don't care what Scripture teaches. You've already decided what you WANT to believe, so all you're doing now is looking for "verses" to support your a priori belief, where you PROJECT the word "conditional" all over the place.
I can't find anywhere in Scripture which speaks about "quits hearing and believing".
You are simply engaging in assumption after assumption to try to justify your initial assumption that "one can lose their salvation".
Jesus says that if one believes they HAVE eternal life.
If one can "lose" it, then they never had "eternal life" in the first place.
It also makes salvation dependent on man, rather than God.
But Christ is our SHEPHERD, not merely our "road sign".
Therefore gaining initial possession of the promise of eternal life is CONDITIONAL upon hearing and believing and maintaining that promise is CONDITIONAL upon continuing to hear and believe.
That's only because you ASSUME that hearing and believing are controlled by man, and not by God.
If it makes sense that one must first conditionally hear and believe to initially possess that promise then it only makes sense one must conditionally keep on hearing and believing to keep on possessing that promise.
This is nothing but unBiblical rationalization.