Look at it this way : As a long-term investor, once you have done the due-diligence / initial study and buy into a company at a particular price (either lumpsum or over a period of time), it becomes a part of your equity portfolio. From then on, the decision on your part as an investor will be one of the following:
i) Buy or add more if the company is doing well over a period of time or in a general mkt fall
ii) Sell if the company is not doing well, or sector doesn’t hold promise
iii) Switch to another company when you find one and the latter (newer idea) holds more promise than the one you already hold.
iv) Sell when you need the money (or in case of an emergency)
In either of these cases, the initial buy price (or even your last/average buy price) is not a determinant. So, in a sense, the buy price should not matter to you as an investor from that point on. Besides, if one is fixated with the last buy price, biases (like recency bias, sunk cost fallacy etc) may set in and hold you back in taking further decisions on your portfolio related to that company, like adding more qty if there is a general market fall (no fault of the company) or sell/switch to a better company.
As part of portfolio management though, some investors use either the average buy price or the current price of the scrip - to decide how much quantity they want to hold compared to overall portfolio (for ex: one may decide to limit the holding of that particular scrip to 10% of the overall portfolio).
My 2c. Hope this helps.