Not at all. Scientific theories may be falsified (disproven) at any time, by new evidence. Theories may be revised, or new evidence explaning phenomena may be found.

A great example is from physics:
Newton formalized the theory of Universal Gravitational Attraction — an instantaneous attractive force acting upon every object in the universe (and proportional to distance).

Einstein revised this by introducing the limiting factor of the speed of light. PREDICTED gravity would attract (bend) light — this was verified by observers during a solar eclipse. Stars that should have been occluded by the solar disk were visible!
~~~~~~~~~~~~~

Another “adjustment” to the theoretical explanation of the cosmos with Newton’s laws, was the explanation of increased mass at higher velocities, and time-dilation at high velocities. These were not even addressed by Newton, yet were PREDICTED by Einstein’s theories, and OBSERVATION confirmed those theoretical predictions.
So the previous theories were AMENDED when special conditions were known to exist.
~~~~~~~~~~~~~~

Another classic example of a theory’s logic was Mendeleev’s theory of the organization of the chemical elements.
Prior to Mendeleev, there had been numerous attempts to order the elements. Several hypotheses were advanced, but none accounted for all observed phenomena or chemical reactivity.

Mendeleev arranged the known elements by mass / atomic number (number of protons), and put them in groups according to their outermost shell electron count (valence electrons).
When completed, there were several “gaps” where elements should, according to Mendeleev’s theory, exist. At later dates these elements were identified, and were found to have the physical and chemical properties predicted.
~~~~~~~~~~~~~~

Quite a lot was known about breeding and trait inheritance, yet it was not scientifically studied with controlled experiments until Friar aGregor Mendel devised, carried out, analyzed and formulated specific methods of inheritance. His experiments with peas established the basis for genetics — a true theory and explanation of previous “theories” of inheritance.
~~~~~~~~~~~~~~

There are (almost) innumerable instances of theories being disproven, discarded, modified or altered based upon new or more precise evidence.